Year 7 Science · Unit 3 · Lesson 18

Work and Efficiency

Foundation Worksheet

Name

Date

Class

Learning Goals

Distinguish between the physics definition of work and the everyday meaning.
Match key vocabulary — work, Joule, efficiency, friction, useful energy, waste energy — to their definitions.
Sort situations into "work is done" and "no work done" using the physics definition.

Warm Up

Sort it!

Write each scenario from the pool into the correct category box below. A force must cause movement in the same direction for physics work to be done.

Lifting a schoolbag off the floor Holding a heavy box still for 2 minutes Pushing a trolley across a supermarket Sitting in a chair doing homework Pushing against a locked door that does not move A hammer driving a nail into wood A weightlifter holding a barbell overhead — stationary A bulldozer pushing soil across a building site A student sliding a book across a desk Standing in a queue without moving

Work IS done (physics)

No work done (physics)

Your Turn

Match each term to its definition

Draw a line connecting each term on the left to its correct definition on the right. Or write the matching letter next to each term.

Term	Your answer	Definition
Work (physics)		A. The percentage of input energy that becomes useful output energy
Joule		B. Energy output that actually does the intended job — e.g. kinetic energy from a motor
Efficiency		C. A force that opposes movement between surfaces, converting kinetic energy to heat
Friction		D. Energy transferred when a force causes movement in the direction of that force
Useful energy		E. Energy that is lost to less useful forms — usually heat or sound — during a transformation
Waste energy		F. The SI unit of energy and work — abbreviated J

Show What You Know

1. A student says: "I worked really hard studying for three hours, so I must have done a huge amount of physics work." Is the student correct? Explain using the physics definition of work.

Recall 2 marks

2. A petrol car engine uses 1000 J of chemical energy from fuel and produces 250 J of useful kinetic energy. Calculate the efficiency of the engine and state where the remaining energy goes.

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?