Work and Power – GCSE Physics

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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:

An illustration comparing the concepts of work and power in two sectors: transportation (airplanes, cars, ships) and sports & fitness (people cycling, playing basketball, and exercising).

An illustration comparing work and power in technology (appliances) and energy production (power plants).

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:

An image showing the formula for work in physics: E = F × d, where E is energy, F is force, and d is distance.

Where,

  • E = Work done
  • F = Force
  • d = Distance

certified Physics and Maths tutorSolved 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: 

Step #1: Given

    • F = 200N
    • d = 3m

Step #2: Using the formula:

An image showing the work-energy formula and an example calculation: E = 200 × 3 = 600J.

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:

An image showing the power formula in physics: P = E / t or P = W / t, where P is power, E is energy, W is work, and t is time.

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.

An image showing a phone with a low battery being charged, illustrating the concept of work and power in transferring energy from a power source to the phone.

  • When we push a box, energy is used to do work, and the rate at which this energy is used is called power.

An image showing a person pushing a box, demonstrating the concept of work and power in physics as force is applied over a distance.

certified Physics and Maths tutorSolved 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:

An image showing the formula for power in physics: P = W / t, with an example calculation where work (W) is 1200 joules and time (t) is 6 seconds, resulting in P = 200 watts.

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

certified Physics and Maths tutorSolved 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:

An image showing the formula for work in physics: E = F × d, where E is energy, F is force, and d is distance.

Step #3: Calculate the Work:

An image showing the work-energy formula with an example: E = 30 × 5, resulting in E = 150 joules.

Work done is 150J.

Final Answer: 150J

certified Physics and Maths tutorSolved 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:

An image showing the power formula in physics: P = W / t, where P is power, W is work, and t is time.

Step #3: Calculate the Work:

An image showing the formula for calculating power in physics: P = 900 / 10, resulting in P = 90.

The Boy’s power output is 90 watts.

Final Answer: 90 watts

certified Physics and Maths tutorSolved 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:

An image showing the formula for work in physics: E = F × d, where E is energy, F is force, and d is distance.

Step #3: Calculate the Work:

An image showing the work-energy formula: E = 50 × 10, resulting in E = 500 joules.

Work done is 500J.

Final Answer: 500J

certified Physics and Maths tutorSolved 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:

An image showing the power formula in physics: P = W / t, where P is power, W is work, and t is time.

Step #3: Calculate the Work:

An image showing the power formula: P = 500 / 20, resulting in P = 250 watts.

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

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