⚡ Understanding Power and Work

Learn how work is done, how power measures the rate of doing work, and how both ideas connect to daily life and physics numericals.

Class 8 Physics Work Done Power Energy Numericals

📌 Learning Map

🎯 Learning Objectives

• Understand the meaning of work in physics.
• Learn the formula of work done.
• Understand power as the rate of doing work.
• Apply formulas in simple numerical problems.

🧩 Competencies

• Conceptual Understanding
• Numerical Skills
• Logical Thinking
• Application Skills

📊 Learning Outcomes

• Defines work and power correctly.
• Identifies when work is done.
• Uses W = F × d correctly.
• Uses P = W ÷ t correctly.

🌈 5W-1H + 1U

🔴 What: Work is done when a force moves an object through a distance.

🟠 Why: It helps us understand how force causes motion and energy transfer.

🟡 When: Work is done only when displacement takes place in the direction of force.

🟢 Where: Used in lifting, pushing, pulling, running machines and daily activities.

🔵 Who: Students, engineers, athletes, workers and scientists use this concept.

🟣 How: Work = Force × Distance and Power = Work ÷ Time.

⚫ 1U: If there is force but no displacement, work done is zero.

Animated Idea: Force + Displacement = Work

📦

➡

When force moves the box through a distance, work is done.

🖼️ Image Placeholder

Replace the image URL below with your own Blogger image URL if needed.

Image idea: A person pushing a box, lifting a weight, or a machine doing work.

▶ Watch: Understanding Power and Work

Watch the video lesson and then try the interactive quiz and calculators.

YouTube video link used: https://youtu.be/WOvvENDsOwo?si=1SXJyMdbIUD5O32Z

🧮 Important Formulae

Work Done = Force × Distance

W = F × d

Unit of work: Joule (J)

Power = Work Done ÷ Time

P = W ÷ t

Unit of power: Watt (W)

Example 1: Work Done

A force of 20 N moves a box through 5 m. Find the work done.

Formula: Work Done = Force × Distance

Work Done = 20 × 5

Work Done = 100 J

Example 2: Power

A machine does 600 J of work in 30 s. Find its power.

Formula: Power = Work Done ÷ Time

Power = 600 ÷ 30

Power = 20 W

Quick Memory

Work needs both force and displacement.

🔢 Interactive Calculator

Work Done Calculator

Enter force and distance.

Power Calculator

Enter work done and time.

Find Time

Enter work done and power.

✅ Work and Power Quiz

Select the correct answer and click submit to check your score.

1. Work is done when: Force causes displacement Only force is applied Object does not move

2. Formula of work done is: Force × Distance Work ÷ Time Mass × Speed

3. SI unit of work is: Joule Watt Newton

4. Power is: Rate of doing work Force only Distance only

5. Formula of power is: Work ÷ Time Force × Distance Distance ÷ Time

6. SI unit of power is: Watt Joule Metre

7. If force = 10 N and distance = 4 m, work done is: 40 J 14 J 6 J

8. If work = 100 J and time = 5 s, power is: 20 W 500 W 105 W

9. If a wall does not move when pushed, work done is: Zero Maximum Negative always

10. A more powerful machine does: Same work in less time No work Only slow work

🧠 HOTS Questions

Click each question to reveal the answer.

1. Why is no work done when a heavy wall is pushed but it does not move?

Because displacement is zero. In physics, work needs force and displacement.

2. Why does climbing stairs require work?

Because force is applied to lift the body upward through a height.

3. Why is power important in machines?

Power tells how fast a machine can do work.

4. Can two machines do the same work but have different power?

Yes. The machine that completes the same work in less time has greater power.

5. Why is the unit of power called watt?

Watt is the SI unit of power and represents one joule of work done per second.