What a learner can do afterwards
- Calculates work done when a force drags, lifts or pushes something a stated distance
- Converts between joules, watts and seconds to find any missing quantity
- Explains why carrying a bag horizontally does no work against the lifting force
1 · Read
Work has a strict scientific meaning for you: force times distance moved along that force, in joules. Push a wall all day with no movement and you do zero work, however tired you feel. Only the distance along the force counts.
Carrying a shopping bag along a flat corridor does no work against the lifting force, because the motion runs sideways to the upward pull. Lift the same bag up the stairs and it counts, since the movement follows the force.
Power tells you how fast work gets done: power = work divided by time, in watts, and one watt is one joule per second. A motor lifting a 40 kg crate 3 m in 5 s: weight 400 N, work 400 times 3 = 1200 J, power 1200 divided by 5 = 240 W. Cover and rearrange to find any missing quantity.
Juggling joules, watts, and seconds is one equation in three outfits. Write units at every step: newtons times metres give joules, joules divided by seconds give watts. The units check the maths for you.
Force along the distance makes joules, joules per second make watts.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.