Work and Power – 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
Solved ExampleProblem: 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:
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:
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:
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:
Step #1: Identify the Term
- E = 900J
- t = 10s
Step #2: Apply the formula:
Step #3: Calculate the Work:
The Boy’s 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:
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:
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:
No work is done if:
- There’s 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