Work: Transferring Energy with a Force — Drills · Grade 8 Science

Chapter: Work & Machines

What these drills covers

By the end of Work: Transferring Energy with a Force you should be able to:

6 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: work, joule, displacement, model, evidence, system boundary, assumption.

Problem 1

A 9 N force acts along 2 m of movement. Find work.
Answer and explanation

18 J

9 × 2 = 18.

Problem 2

A force does 30 J of work along a 5 m displacement. Find the force.
Answer and explanation

6 N

30 ÷ 5 = 6.

Problem 3

A force of 20 N moves an object 5 m in the direction of the force. How much work is done, in joules?
Answer and explanation

100 J

work = force × distance = 20 × 5 = 100 J.

Problem 4

How much work in joules is done lifting a 15 N weight through 3 m?
Answer and explanation

45 J

15 × 3 = 45 J.

Problem 5

You push hard against a wall that does not move. The work done on the wall is
  1. large
  2. zero
  3. negative
  4. equal to your force
Answer and explanation

zero

Work requires movement in the direction of the force; with no displacement, no work is done on the wall.

Problem 6

Explain why holding a heavy box still requires effort but does no work in the scientific sense.
Answer and explanation

Work in physics is force multiplied by the distance moved in the direction of that force, and a stationary box moves no distance, so the work done on it is zero. The effort felt comes from muscle fibres repeatedly contracting and using chemical energy inside the body, which is a real energy cost but not work done on the box.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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