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Grade 9 Intermediate About 15 min Version 1 Awaiting review Premium

Work done in lifting loads

In science, work is done when a force moves something in the direction of the force: work = force × distance, measured in joules (J). To lift a box at a steady speed you must push up with a force equal to its weight (mass × g). So lifting a heavier box, or lifting it higher, takes more work. Power is how quickly work is done: power = work ÷ time, measured in watts (W). One watt is one joule per second.

What you will learn

  • Calculate work done using work = force × distance.
  • Show how mass and height affect the work done in lifting.
  • Calculate power and explain why a quicker lift needs more power.

Before you start

  • Know that weight = mass × g.

Materials

  • Boxes of 1 kg, 2 kg, 5 kg and 10 kg

Equipment

  • Shelves at 0.5 m, 1 m, 1.5 m and 2 m
  • Metre rule and stopwatch

Procedure

  1. Lift the 2 kg box and the 10 kg box to the same height and record both.
  2. Lift one box to two different heights and record both.
  3. Lift the same box to the same height in 1 s and in 8 s and compare the power.

How this simulation is simplified

  • g is taken as 10 N/kg.
  • The box is lifted at a steady speed, so the lifting force equals its weight.