Rotational Force โ GCSE Physics
Introduction
- Rotational force is the force that causes an object to rotate around a point or axis (pivot point) instead of moving in a straight line.
- This force is also called:
Moment
Torque
- Rotational force plays a crucial role in daily life and machines because it helps us turn, rotate, or twist objects using force applied at a distance from the axis.
Daily-Life Example:
What is Moment?
- A Moment (in physics) refers to the rotational effect produced by a force acting at a distance from a pivot point (axis of rotation).
- It is essentially a turning force that causes an object to rotate.
- Moment is another name for rotational force.
Moment Formula:
Where:
- M = Moment in – Nm
- F = Force applied in – N
- d = Perpendicular distance from the pivot in – m
Solved Example
Solved ExampleProblem: A student applies a force of 20 N at the end of a spanner to loosen a nut. The distance from the nut to the point where the force is applied is 0.3 m. Calculate the moment (rotational force) about the nut.
Solution:ย
Step #1: Given
- F = 20N
- d = 0.3m
Step #2: Using the formula:
The moment about the nut is 6 Nm.
Final Answer: 6 Nm
How Is Moment Related To Torque?
- Moment tells us how strong the turning effect of a force is where torque is a special type of moment that not only makes something turn but also causes it to spin faster or slower (rotational acceleration) around an axis.
- Torque is another name for moment; both mean the turning effect of a force about a point.
- Torque is a specific term for the turning effect around the axis of rotation, especially used in mechanics, engines, and rotational systems.
- Example: When you push a door to open it, you are using moment and torque together: Moment explains how your push causes the door to rotate around its hinges and torque explains how strong that rotation will be.
Formula For Both:
When the force is perpendicular to the pivot point:
Where:
- F = Force applied in – N
- d = Perpendicular distance from the pivot in – m
When the force is at any angle or not perpendicular:
Where:
- F = Force
- r = Distance from axis to point where force is applied.
- ฮธ = Angle between F and r.
How to Calculate Rotational Force?
- Calculation for rotation in terms of moment involves finding how much a force causes an object to turn around a point or pivot.
To Calculate Moment in Physics, We Follow These Simple Steps:
- Step#1: Identify the given values.
- Step#2: Apply the formula and plug in the values.
- Step#3: Calculate the moment.
Solved Example
Problem: A force of 12 N is applied perpendicularly at a distance of 0.4 m from the hinge of a gate. Calculate the moment.
Solution:ย
Step#1: Identify the given values:
Given
- F = 12N
- d = 0.4m
Step#2: Apply the Formula and plug in the values:
The formula for moment is:
Now plug in the values:
Step#3: Calculate the Moment:
The moment is 4.8 Nm in the anticlockwise direction.
Final Answer: 4.8 Nm
Solved Example:ย
Problem: A flagpole painter applies a force of 150 N perpendicularly on a brush attached to a rope that is tied 250 cm from the base of the flagpole to rotate and clean it. Calculate the moment about the base of the flagpole.
(Rotational Force GCSE Questions)
Solution:ย
Step#1: Identify the given values:
Given
- F = 150N
- d = 250cm
Step#2: Apply the Formula and plug in the values:
Convert cm to m:
The formula for moment is:
Now plug in the values:
Step#3: Calculate the Moment:
The moment about the base of the flagpole is 375 Nm in the anticlockwise direction.
Final Answer: 375 Nm
Solved Example
Problem: A shopkeeper pushes down on the handle of a heavy shop shutter with a force of 400 N perpendicular to it, producing a moment of 800 Nm about the hinge. Find the distance from the hinge where the force is applied.
Solution:ย
Step#1: Identify the given values:
Given
- F = 400N
- M = 800Nm
Step#2: Apply the Formula and plug in the values:
The formula for moment is:
Rearranged it:
Now plug in the values:
Step#3: Calculate the Moment:
The perpendicular distance is 2 meters.
Final Answer: 2 Meters
Solved Example
Problem: Child B weighs 350 N and sits 1.6 m from the pivot on a balanced seesaw. Calculate the moment of child B about the pivot. Give your answer in newton-metres (Nm).
Solution:ย
Step#1: Identify the given values:
Given
- F = 350N
- d = 1.6m
Step#2: Apply the Formula and plug in the values:
The formula for moment is:
Now plug in the values:
Step#3: Calculate the Moment:
The moment is 560 Nm.
Final Answer: 560 Nm.
Frequently Asked Questions
Solution:
Rotational force (torque or moment) is the tendency of a force to cause an object to rotate around a point or axis.
Solution:
Yes, both measure rotational effect of a force.
Solution:
Formula for moment:
M = F ร d
Solution:
Newton-meter (Nm).
Solution:
- If the force causes clockwise rotation – moment is negative.
- If it causes anticlockwise rotation – moment is positive.
Solution:
The moment increases, making it easier to rotate heavy objects.
Solution:
Opening a door, using a spanner, turning a steering wheel, or pushing a swing are daily examples of rotational forces.
Red-Shift: Origin of the Universe โ GCSE Physics
Introduction
- In Astronomy, redshift is used to describe celestial objects and distant galaxies that are moving away from Earth.
- Redshift is a phenomenon where wavelength of light emitted from a distant galaxy that is moving away from is shifted towards the red end of spectrum.
- Redshift is an evidence of the big bag theoryโs saying that universe is continuously expanding that is why its study become important.
What is Redshift and Examples
Redshift
- Red Shift is basically a phenomenon related to the origin of universe in which the wavelength from the distant celestial objects is stretched shifting it to the red end of the spectrum. This proves the fact that Universe is continuously expanding.
- The visible light spectrum show us the visible wavelengths and those exact wavelengths that are absorbed by the gaseous molecules present on the Sun. These molecules absorb some part of the light that reach at the surface of Earth. When examined we can see that those black lines shown in the visible light spectrum is the part that shows the absorbed wavelengths.
- It is observed that these black lines in spectrums from different galaxies and stars are not the same instead they are shifted towards the red end. That is called Redshift. This happens because the Universe is expanding and the galaxies are moving away from earth, the farthest the galaxy the more Red shift is observed in spectrum. This is related to origin of the Universe.
- The Siren bus is going away from the observer 1 and towards the observer 2, we can see in the diagram clearly that the resource is producing sound waves of more frequency towards the 2nd observer and the wavelength is low. On the other hand the sound waves experienced by the 1st observer are of lesser frequency but higher wavelength.
- Suppose there is a 3rd observer who experiences the sound waves from the siren bus while he/she is in car and with same velocity as that of the siren bus, then there will be no change in the sound waves experienced by that observer.
Redshift and Origin of Universe
- Redshift is fundamental concept for understanding the origin and expansion of Universe.
- In 1969, Edwin Hubble discovered that there is relationship between Redshift of the light travelling from distant galaxies and expansion of universe.
- Due to the expansion of Universe, the light wavelength travelling through it is stretched resulting into Cosmological Redshift.
- The Doppler Redshift arises from the relative motion in space but the Cosmological Redshift is caused by the expansion of Universe itself.
- By the observations of distant galaxies through redshift, it is concluded that the galaxies are made a million years ago from Big Bang.
Origin of The Universe:
Big Bang Theory:
- According to the Big Bang Theory suggested in 1920’s the whole Universe and all matter in it started as a tiny point of concentrated energy about 13.5 billion years ago. The Universe expanded from this point and is still expanding. As the Universe expanded, gravity caused the matter to clump together to form the stars and other celestial objects.
Cosmic Microwave Radiations:
- Astronomers discovered radio waves coming all over from the Universe. Astronomers realized that this was the radiation predicted in Big Bang Theory. In the beginning of Universe huge amount of radiations were released according to Big Bang Theory. The wavelength of these radiation is now increased and is only detectable as Microwave radiations called as Cosmic Microwave Background(CMD).
Steady state Theory:
- The theory was suggested in 1948. This theory says that the Universe has already existed and is expanding. New matter is continuously created as the Universe expands.
Frequently Asked Questions
Solution:
Redshift is the phenomenon where the wavelength of light is stretched coming from the distant galaxies. It basically happens because of the galaxies moving away from us and the expansion of Universe.
Solution:
Redshift is measured by observing Visible Light Spectrum.
Solution:ย
Redshift is a type of Doppler effect where the light gets stretched and its wavelength becomes longer and frequency lowers.
Solution:
Redshift observed from distant galaxies tells us about the universeโs expansion and origin of the universe and its evolution.
Solution:
CMB is Cosmic Microwave Background, means that microwave radiations are coming from all over the universe which were radiated in the beginning of it through Big Bang explosion.
Renewable and Non-Renewable Resources โ GCSE Physics
Introduction
- Studying Renewable and Non-Renewable Resources is vital because it helps us understand our energy resources. By studying them we get to know that how we can use them wisely.
- Studying about the differences between Renewable & Non-Renewable resources is crucial so that we can sustainably use our resources without the environmental damage.
- Understanding about these Energy Resources includes understanding environmental concepts too as the use of these resources is dependent of these environmental factors.
Renewable Resources
- Renewable Resources can be easily replaced, therefore we can continuously use them. Examples include – Sunlight, Water, Geothermal Energy, Wind etc.
- These resources can be used sustainably. But using them at large scale is costly.
- As the population increases the demand of these resources is increasing too.
- These resources are weather dependent. Suppose the generation of solar power which is totally dependent of sunlight but the conditions may vary according to the season of the year, time of the day and existing weather conditions.
Advantages and Disadvantages of Renewable Resources
Advantages
- Reduce harmful green house gas production.
- Clean air and fresh water.
- These resources are constantly renewed by nature itself and are sustainable.
- Long-term availability.
- Minimal or no pollution.
Disadvantages
- These resources are weather dependent that means energy is produced inconsistently.
- Their storage is difficult and expensive if large amount of energy is generated.
- The energy production from natural resources like sunlight and wind are location specific limiting their overall performance.
- More Land usage.
Non-Renewable Resources
- Non Renewable Resources cannot be easily renewed because they are finite and thus we need to use them wisely. Examples include- Fossil Fuels (coal), Oil, Natural Gas.
- These resources are limited and thus canโt be sustainably used.
- These resources are directly extracted from Earth. After exraction they are converted to fulfill the needs.
- Burning these resources is harmful for our environment.
Advantages and Disadvantages of Non- Renewable Resources
Advantages
- High output
- Easily Affordable
- Reliable
- Easily stored, transported because there are well developed techniques and infrastructure for these purposes
Disadvantages
- Pollution: Burning these resources like coal produces harmful gases like Carbon Dioxide, Nitrogen Oxides and Sulphur dioxides.
- These resources produce significant amount of the gases which causes acid rain and climate.
Difference between Renewable and Non- Renewable Resources
Frequently Asked Questions
Solution:
They difference between them is that Renewable Resources can be renewed they are naturally available and can be reused like Wind Energy, but on the other hand Non-Renewable resources are finite and we need to them wisely because they cannot be renewed like fossil fuels.
Solution:
Solar Energy, Wind Energy, Water and Geothermal Energy.
Solution:ย
Yes, Non-Renewable enrgy resources like fossil fuels when burn produce harmful green house gases and results in air pollution.
Solution:
Renewable energy resources are sustainable and can be used for long time providing a secure future, but Non-Renewable resources are limited and have environmental issues too.
Solution:
Geothermal Energy.
Solution:ย
Studying Renewable and Non-Renewable Resources is vital because it helps us understand our energy resources. By studying them we get to know that how we can use them wisely.
Distance Time Graph โ GCSE Physics
Introduction
- Motion is the change in position of an object with respect to time.
- The three fundamental quantities that describe Motion are:
Distance: It is the total path length covered by an object, regardless of direction.
Time: It is the duration over which Motion occurs.
Speed: It tells us how fast an object moves.
What is Speed and How is it Measure?
- Speed is the measure of how fast an object moves.
- It defined as the distance traveled per unit of time.
- It is a Scalar Quantity.
- Speed can be measured using the formula:
Common SI Units:
- Meters per second (m/s)
- Kilometers per hour (km/h)
- Miles per hour (mph)
Solved Example
Problem: If a bike travels 150 meters in 10 seconds, what’s the speed of bike?
Solution:ย
Step #1: Given
- Distance: 150 m
- Time Taken: 10s
Step #2: Using the formula:
Step #3: Putting the values and solve:
So, the speed of the bike is 15 meters per second (m/s)
Final Answer: 15 m/s
Speed, Distance and Time Triangle
- The Speed, Distance and Time Triangle is an easy way to remember the relationship between speed, distance, and time.
- It helps in calculating one quantity when the other two are known.
How to use Triangle:
- To Find Speed: Cover “S” and the formula is,
- To Find Distance: Cover “D” and the formula is,
- To Find Time: Cover “T” and the formula is,
What is a Distance-Time Graph?
- A Distance-Time Graph is a graphical representation of how distance changes over time.
- It helps visualize the motion of an object.
Features of a Distance-Time Graph:
- X-axis (Horizontal) โ Represents Time (seconds, minutes, hours).
- Y-axis (Vertical) โ Represents Distance (meters, kilometers).
- Slope of the Graph โ Represents Speed.
Graphs for various types of body motion:
- In Graph, the Gradient of the line at any point tell us the Speed of the object is travelling.
- Mathematically,
How to Calculate Speed from Distance-Time Graph?
Steps to Calculate Speed from the Graph:
- Step#1: Observe the Graph.
- Step#2: Identify Two Points on the Graph.
- Step#3: Find the Change in Distance (ฮd).
- Step#4: Find the Change in Time (ฮt).
- Step#5: Calculate the Speed using formula,
Case 1: For Stationary body, it observed that the object is not moving. Since distance remains the same over time,
Case 2: For Uniform body, the graph is a straight line and the speed is constant.
Case 3: For Non-Uniform body, speed varies over time, so find instantaneous speed by calculating the slope of the tangent at a given point.
If Curved upwards โ Acceleration (speed increasing).
If Curved downwards โ Deceleration (speed decreasing).
Solved Example
Problem: The distance-time graph of an object shows a slope at 20 meters for 4 seconds. What is the speed of the object?
Solution:ย
Step #1: Observe the Graph,
- The Body is in Uniform Motion.
Step #2: Identify Two Points on the Graph:
- At t1 = 0s, d1 = 0m.
- At t2 = 4s, d2 = 20m.
Step #3: Change in Distance (ฮd):
Step #4: Change in Time (ฮt):
Step #5: Calculate the Speed:
Final Answer: 5 m/s
Solved Example
Problem: The Distance-Time Graph of an object shows a flat horizontal line at 5 meters for 10 seconds. What is the speed of the object?
Solution:ย
Step #1: Observe the Graph,
- The line is horizontal in the graph, so Distance does not change over time.
Step #2: Identify Two Points on the Graph:
- At t1 = 0s, d1 = 5m.
- At t2 = 10s, d2 = 5m.
Step #3: Change in Distance (ฮd):
Step #4: Change in Time (ฮt):
Step #5: Calculate the Speed:
Final Answer: 0 m/s
Frequently Asked Questions
Solution:
Use the formula: Speed = Distance รท Time. On a graph, calculate the slope by dividing the vertical change (distance) by the horizontal change (time).
Solution:
Calculate the area under the graph line. Use basic shapes like rectangles and triangles to measure the area, which gives you the distance.
A steeper line shows a higher speed โ the object is moving faster.
Solution:
It means the object is stationary โ it is not moving.
Solution:
Yes, when the slope changes or becomes curved (not shown in this example), it indicates acceleration or deceleration.
Practice regularly, look at real exam questions, and use worksheets. Pay attention to axes labels, slope changes, and units.
Work and Power โ GCSE Physics
Introduction
- Work and Power are fundamental concepts in physics that describe how forces affect motion and energy transfer.
- Understanding these concepts is essential in physics and engineering that help us understand and quantify energy transfer, efficiency, and mechanical performance in real-world applications.
Real-Life Applications of Work and Power:
What is Work and How is it Measure?
- Work is done when a force causes an object to move in the direction of the force.
- It is defined as the product of force and the distance moved by an object in the direction of the force.
- It is a Scalar Quantity.
- The SI unit of work is the joule (J).
- Work can be measured using the formula:
Where,
- E = Work done
- F = Force
- d = Distance
Solved Example
Problem: Danny is moving a box weighing 300N. He pulls it 3 m along a sloping ramp using a force of 200N. Calculate the work Danny does.e Resultant Force?
Solution:ย
Step #1: Given
- F = 200N
- d = 3m
Step #2: Using the formula:
Danny does 600 joules of work.
Final Answer: 600 joules
What is Power and How is it Measure?
- Power is the rate at which work is done or energy is transferred or converted per unit time.
- It measures how quickly energy is used, generated, or transferred.
- It is a Scalar Quantity.
- The SI unit of power is the watt (W).
- Power can be measured using the formula:
Where,
- P = Power
- E = Energy Transferred
- t = Time
- W = Work done
Example:
- When we charge our phone, electrical energy is transferred over time, and this rate of energy transfer is called power.
- When we push a box, energy is used to do work, and the rate at which this energy is used is called power.
Solved Example
Problem: A motor does 1200 joules of work in 6 seconds. What is the power of the motor?
Solution:ย
Step #1: Given
- E = 1200J
- t = 6s
Step #2: Using the formula:
The Power of the motor is 200 watts.
Final Answer: 200 watts
How to Calculate Work and Power?
Steps to Calculate Work:
- Step #1: Identify the Term
- Step #2: Apply the formula
- Step #3: Calculate the Work
Steps to Calculate Power:
- Step #1: Identify the Term
- Step #2: Apply the formula
- Step #3: Calculate the Work
Solved Example
Problem: A worker pushes a cart with a 30 N force over 5 m in the same direction. What is the work done?
Solution:ย
Step #1: Identify the Term
- F = 30N
- d = 5m
Step #2: Apply the formula:
Step #3: Calculate the Work:
Work done is 150J.
Final Answer: 150J
Solved Example
Problem: A boy runs up a flight of stairs and does 900 joules of work in 10 seconds. What is his power output?
Solution:ย
Step #1: Identify the Term
- E = 900J
- t = 10s
Step #2: Apply the formula:
Step #3: Calculate the Work:
The Boyโs power output is 90 watts.
Final Answer: 90 watts
Solved Example
Problem: A man pushes a box with a horizontal force of 50 N for a distance of 10 m along the floor. Calculate the work done.
Solution:ย
Step #1: Identify the Term
- F = 50N
- d = 10m
Step #2: Apply the formula:
Step #3: Calculate the Work:
Work done is 500J.
Final Answer: 500J
Solved Example
Problem: A machine does 5000 joules of work in 20 seconds. Calculate the power of the machine.
Solution:ย
Step #1: Identify the Term
- E = 500J
- t = 20s
Step #2: Apply the formula:
Step #3: Calculate the Work:
The Power of the machine is 250 watts.
Final Answer: 250 watts
Frequently Asked Questions
Solution:
Work is done when a force moves an object in the direction of the force.
Solution:
The SI unit of work is the joule (J).
Solution:ย
No work is done if:
- Thereโs no movement.
- The force is perpendicular to the direction of movement.
Solution:
Power is the rate at which work is done or energy is transferred.
Solution:
The SI unit of power is the watt (W).
Solution:
Work is a scalar quantity.
Solution:
Formula for Work:
E = F x d
Energy Efficiencyโ GCSE Physics
Introduction
- The concepts of Energy and Power Efficiency are essential for understanding how systems use resources and how to optimize them for better performance and sustainability.
- Efficiency is a way of describing how good a machine is at transferring energy into useful forms.
What is Energy Efficiency?
- Energy Efficiency measures how effectively a system, device, or process converts input energy into useful output energy to perform a desired task.
- It measures how efficiently Energy is converted into useful work while minimizing waste.
- Formula:
where,
Example:
LED Bulb and Incandescent Bulb:
- An LED bulb converts about 80-90% of the electrical energy into light, with very little wasted as heat.
- An Incandescent bulb, on the other hand, converts only about 10% of the electrical energy into light โ the rest is lost as heat.
- The LED bulb is more energy-efficient.
What is Power Efficiency?
- Power efficiency is the ratio of useful output power to the total input power supplied to a system or device.
- It measures how efficiently Power is converted into useful work while minimizing waste.
- Formula:
Where,
- Output power is the power used to perform the desired task.
- Input power is the total power supplied to the system.
- The rest is usually lost as heat, noise, or vibration.
Example:
- Fan A is more power-efficient because it converts more of the input power into useful mechanical power, while wasting less power as heat, noise, or friction.
How to Calculate Efficiency?
- Efficiency tells us how well a device or system converts input energy or power into useful output.
- Itโs usually expressed as a percentage.
Formula for Energy Efficiency:
Formula for Power Efficiency:
Steps to Calculate Efficiency:
- Step#1: Find the input value (energy or power supplied to the system).
- Step#2: Find the useful output value (energy or power used for the intended purpose).
- Step#3: Apply the formula.
- Step#4: Multiply by 100 to convert it into a percentage.
Solved Example
Problem: A light bulb takes 100 joules of electrical energy and produces 60 joules of light energy. The rest is lost as heat. Calculate the energy efficiency of the light bulb.
Solution:ย
Step #1: Find the input value
- Total Input Energy = 100 J
Step #2: Find the useful output value:
- Useful Output Energy = 60 J
Step #3: Apply the formula:
Step #4: Multiply by 100:
The light bulb has an energy efficiency of 60%.
Final Answer: 60%
Solved Example
Problem: A water pump uses 500 watts of electrical power and delivers 400 watts of useful mechanical power to pump water. Calculate the power efficiency of the pump.
Solution:ย
Step #1: Find the input value
- Total Input Power = 500W
Step #2: Find the useful output value:
- Useful Output Power = 400W
Step #3: Apply the formula:
Step #4: Multiply by 100:
The water pump has a power efficiency of 80%.
Final Answer: 80%
Frequently Asked Questions
Solution:
Efficiency measures how well something (a machine, device, or system) converts input (like energy) into useful output without wasting resources.
Solution:
We can reduce unwanted energy transfers by using lubrication to reduce friction, insulation to prevent heat loss, and streamlining to reduce air resistance.
Solution:ย
Energy efficiency means using less energy to do the same job. It helps save money and reduces waste.
Example:
- An LED bulb (energy-efficient) gives the same light as an old incandescent bulb but uses much less electricity.
Solution:
Power efficiency measures how well a device converts input power (electricity) into useful output (like light, motion, or computation) without wasting it as heat.
Example:
- A 90% efficient power supply wastes only 10% of electricity as heat, while a 60% efficient one wastes 40%.
Solution:
- Saves money (lower electricity bills).
- Reduces pollution (less energy waste = fewer power plants needed)
Momentumโ GCSE Physics
Introduction
- Momentum is a measure of an objectโs resistance to stopping or changing its motion.
- It helps us to understand motion and explain collisions.
Examples:
What is Momentum?
- Momentum is a measure of how much Motion an object has.
- It represents the quantity of motion an object has and how difficult it is to stop or change its motion.
Key properties:
- A heavier or faster-moving object has more Momentum.
- Momentum depends on both the speed and the direction of motion.
- In a closed system,
- Total momentum before and after a collision remains constant.
Example:
If a Truck and a Car are moving at the same speed, the Truck has more momentum because it has more mass.
A small car hitting a truck wonโt move the truck much, because the truck has way more Momentum.
How to calculate Momentum?
- Momentum depends on Mass and Velocity.
- It is a Vector Quantity.
- Mathematically,
Where,
- p = Momentum
- m = Mass
- v = Velocity
SI Unit: Kilogram-meter per second (kg.m/s)
Solved Example: Momentum GCSE Questions
Problem: A car has a mass of 1000 kg and is moving at a velocity of 20 m/s in North side. Whatโs the Momentum of car in the direction itโs moving?
Solution:ย
Step #1: Given
- m = 1000 kg
- v = 20 m/s
Step #2: Using the Formula:
Step #3: Putting the values:
The car’s momentum is 20,000 kgยทm/s in the direction itโs moving.
Final Answer: 20,000 kgยทm/s
Can Momentum be Positive or Negative?
- Yes, Momentum can be both positive and negative, which indicates the direction of an objectโs motion.
Positive Acceleration:
Directional Reference:
- Object moves in the defined positive direction (e.g., right/east/up/north).
Meaning of Signs:
- +p: Object moves in the positive direction.
Example:
Problem: A 10 kg soccer ball is kicked eastward at 5 m/s.
Solution:ย Let East = positive (+) direction.
ย
Negative Acceleration:
Directional Reference:
- Object moves in the opposite (negative) direction (e.g., left, west, down)
Meaning of Signs:
- โp: Object moves in the negative direction.
Example:
Problem: A 10 kg soccer ball is kicked westward at 5 m/s.
Solution: Let West = negative (-) direction.
Relationship Between Force, Momentum & Acceleration
- Momentum and Acceleration are fundamental concepts in physics, connected through Newton’s Second Law of Motion.
- Momentum depends on velocity, any change in velocity (i.e. acceleration) causes a change in momentum.
But Since,
And Momentum is:
Then change in momentum is:
Substituting this into equation 1,
It says:
- The Force acting on an object is equal to the rate of change of its Momentum.
- If an objectโs momentum changes quickly, a large force is involved.
- If it changes slowly, the force is smaller.
- It can also be written as,
Solved Example: Momentum GCSE Questions
Problem: A cricket ball of mass 0.2 kg is moving at a speed of 25 m/s. What is the momentum of the ball?
Solution:ย
Step #1: Given
- m = 0.2 kg
- v = 25 m/s
Step #2: Using the Formula:
Step #3: Putting the values:
The momentum of the cricket ball is 5 kgยทm/s.
Final Answer: 5 kgยทm/s.
Solved Example: Momentum GCSE Questions
Problem: A car of mass 1200 kg moves backward with a velocity of 5 m/s. What is its momentum?
Solution:ย
Step #1: Given
- m = 1200 kg
- v = 5 m/s
Step #2: Using the Formula:
Step #3: Putting the values:
The momentum of the car is -6000 kgยทm/s.
Final Answer: -6000 kgยทm/s.
Frequently Asked Questions
Solution:
Momentum is a measure of the motion of an object and is the product of its mass and velocity. It is a vector quantity, meaning it has both magnitude and direction.
Solution:
The principle states that in a closed system (no external forces acting), the Total momentum before a collision is equal to the total momentum after the collision
Solution:ย
Formula for Momentum:
p = m x v
Where,
- p = Momentum
- m = Mass
- v = Velocity
Solution:
SI Unit for Momentum is kilogram-meter per second (kgยทm/s)
Solution:
Yes, Momentum is a Vector Quantity which depends on both direction and magnitude.
Difference Between Mass and Weight โ GCSE Physics
Introduction
- To understand how things move, interact, and behave in the physical world, the concepts of Mass and Weight are studied.
What is Mass?
- Mass is how much matter is in an object.
- It is the property of physical objects that measures:
- Inertia: Resistance to acceleration when a force is applied.
- Gravitational influence: Shows the strength of attraction between two objects.
Key Points:
- SI Unit of Mass is Kilogram (Kg).
- It is a Scalar Quantity.
- Mass never changes no matter where the object isโon Earth, on the Moon, or in space.
- It measures Inertia.
Example:
A Rocket has a mass of 2,000 kg, whether itโs on Earth, the Moon, or floating in space, itโs still 2,000 kg.
In all Scenario the Mass of Rocket will remain same (e.g.,2,000 kg)
What is Weight?
- Measure of the Gravitational pull of an object.
- It depends on both the object’s Mass and the local Gravitational Acceleration.
Key Points:
- SI Unit of Weight is Newton (N).
- It is a Vector Quantity.
- It changes with gravity, so weight varies depending on where the object is (Earth, Moon, or space).
- It measures Gravitational force.
Example:
A person with a mass of 60 kg,
Difference between Mass and Weight
Calculating Mass and Weight
Formula for Mass:
Where,
- W = Weight
- g = Acceleration due to Gravity
Formula for Weight:
Where,
- m = Mass
- g = Acceleration due to Gravity
Solved Example
Problem: A bag of rice has a weight of 49 newtons on Earth. What is the mass of the bag?
Solution:ย
Step #1: Given
- W = 49N
- Take gravitational acceleration,
g = 9.8โm/s2
Step #2: Using the formula:
Step #3: Putting the Values:
The mass of the bag of rice is 5 kilograms.
Final Answer: 5 kg
Solved Example
Problem: An object has a mass of 8 kilograms. What is its weight on Earth?
Solution:ย
Step #1: Given
- m = 8kg
- Take gravitational acceleration,
g = 9.8โm/s2
Step #2: Using the formula:
Step #3: Putting the Values:
The weight of the object is 78.4 newtons.
Final Answer: 78.4 N
Frequently Asked Questions
Solution:
Mass is how much matter you have. Weight is how strongly gravity pulls on that matter.
Solution:
Gravity is different on every planet. Your mass doesn’t change, but the force (weight) does.
Example: 60 kg mass
– Earth: 60 x 10 = 600 N
– Moon: 60 x 1.6 = 96 N
Solution:ย
Mass- Kilogram (kg)
Weight- Newton (N)
Solution:
Use W= m x g If you know your mass and the planet’s gravity, multiply them.
Example:
70 kg on Mars (g = 3.7)-70 x 3.7 = 259 N
Solution:
Weight is a force. Mass is how much matter you have.
Weight = gravity pulling on that matter.
Newton's Third Law โ GCSE Physics
Introduction
- Newton’s Third Law of Motion states that, for every action, there is an equal and opposite reaction.
- It explains the fundamental interactions between objects in the universe and help us to understand how forces work in pairs.
Example:ย
What is Newtonโs Third Law of Motion?
- It states that, when two objects interact, the forces they exert on each other are Equal and Opposite.
- Equal refers to the magnitudes of two forces whereas Opposite refers to their direction.
Real-life Examples:
Running:
- Action: Our foot pushes backward against the ground.
- Reaction: The ground pushes us forward with an equal force, making us move.
Bird Flying:
- Action: A birdโs wings push air downward.
- Reaction: The air pushes the bird upward, allowing flight.
What are the Balanced Forces and Action-Reaction Pairs?
Balanced Forces
- These are two or more forces that act on the same object, are equal in size, and opposite in direction, so they cancel each other out.
- No change in Motion or constant Speed (if already moving).
Examples:
Action-Reaction Pairs:
- These are two forces that act on the different objects, are equal in size, and direction, so they do not cancel each other out.
- Cause Motion and Accelerates.
Examples:
What is Collison?
- Collison is an example of a Newtons 3rd law of Motion which states that when two objects collide, both objects exert equal and opposite forces on each other.
- Newtons 3rd Law Applies to Collisions based on:
- Force Pairs During Impact
- Momentum Conservation
- Different Effects Based on Mass
Examples:
Click the links below to learn more about Newton’s Laws of Motion:
Frequently Asked Questions
Solution:
It means that whenever one object pushes or pulls another, the second object pushes or pulls back with the same force in the opposite direction.
Solution:
No. Balanced forces act on the same object. Action reaction forces act on different objects.
Solution:ย
No, because they act on different objects, they do not cancel each other.
Solution:
When you jump off a small boat, you push back on the boat and the boat moves backward.
Solution:
Yes. According to Newtons 3rd law, forces always come in pairs โ Action and Reaction.
Resultant Forces โ GCSE Physics
Introduction
- Force is a push or pull acting on a body.
- A body needs Force to change its state of motion.
- There are number of Forces acting on a body at a same time, so instead of analyzing multiple forces individually, we use the Resultant Force to predict Motion.
- The Resultant Force is the single Force that replaces multiple forces acting on an object, producing the same effect.
Real-life Scenario:
What is Free Body Diagram?
- A Free Body Diagram is a simplified visual representation of an object to visualize the forces acting on a single object (or body).
- It helps analyze the effects of External Forces.
Examples:
Characteristics:
- The arrow points in the direction that the force is acting.
- The length of the arrow shows how strong the force is:
Common Forces in Free Body Diagrams:
- Weight
- Tension
- Friction
- Air Resistance/Drag
What is Resultant Force Equation?
- Resultant Force is the Vector sum of all the individual forces acting on an object.
- It is also called a net force which represent the combined effect of all other forces.
- SI Unit of Force: Newton(N)
Equation 1:
- If F1, F2, F3,โฆ.are the forces acting on a body, the Resultant Force FR is calculated using the formula with positive and negative signs used for pair of opposite forces,
- Where F1, F2, F3, . . . are the Linear Forces acting of the body.
Equation 2:
- If F1 and F2 are the forces perpendicular to each other then their Resultant Force is,
- This consequence can also be calculated geometrically using other methods.
How to Calculate Resultant Force?
Method #1:
- If force acts on a same direction, then the Resultant force is,
Method #2:
- If force acts on a opposite direction, then the Resultant force is,
Solved Example: Method 1
Problem: If Person A pushes a car in the East direction with a Force of 200 N, and Person B also pushes the car in the same direction with a Force of 300 N, what will be the Resultant Force?
Solution:ย
Step #1: Given
- Person A applies Force F1 : 200N
- Person B applies Force F2 : 300N
Step #2: Then the Resultant Force will be:
Final Answer: 500N
Solved Example: Method 2
Problem: If Person A pushes a box to the Left with a Force of 200 N, and Person B pushes the same box to the Right with a Force of 300 N, what is the Resultant Force on the box?
Solution:ย
Step #1: Given
- Person A applies Force F1 : 200N
- Person B applies Force F2 : 300N
Step #2: Then the Resultant Force will be:
Final Answer: 100N
What are Balanced and Unbalanced Force?
Balanced Force:
- Forces acting on an object are equal in Magnitude but opposite in Direction.
- They cancel each other out, so the Resultant Force is Zero.
Characteristics:
- No change in Motion.
- Object or Body remains at rest or continues at Constant Velocity.
Examples:
Unbalanced Force:
- Forces acting on an object are not equal in Unbalanced Force.
- They do not cancel each other out, so the Resultant Force is non-zero.
Characteristics:
- Change in Motion.
- Object or Body accelerates (speed up, speed down or change direction).
Examples:
Frequently Asked Questions
Solution:
A Resultant Force is the overall force acting on an object after all individual Forces are combined.
Solution:
- Add Forces in the same direction
- Subtract it they act in opposite directions. This gives the net force.
Solution:ย
- Resultant force = Larger Force – Smaller Force (if opposite)
- Resultant force = Sum of Forces fil same direction
Solution:
A drawing that shows the size and direction of each force using arrows.
Solution:
When the Resultant Force is not zero this causes movement or change.
Solution:
The object is Balanced. It either stays still or keeps moving at Constant Speed.
Solution:
A Rocket producing 13,000 N thrust and 5,000 N weight then,
Resultant Force is,
FR = FL (Larger Force) – FS (Smaller Force)
FR = 13,000 – 5000 = 8,000 N upwards