Work: Force Times Distance

Lesson 6 of 10 · 7 min · Free, no account needed

What you will learn

Work is energy moved by a force: W = F × d, force in newtons times distance in metres. 1 J = 1 N·m.
A ramp, a pulley or a lever lowers the force but lengthens the distance. The work stays the same.
On a force-distance graph, the work is the area under the line.

Movers use a ramp to load a crate. Does the ramp save energy, or just effort?
First, a guess: drag the marker to the push the ramp needs.
Change the ramp length. Watch the push, the distance and the shaded rectangle.
Drag the crate across the rough floor, 5 m.
The area under the graph grows with every metre.
Moving energy with a force is called work.
Work is the energy a force moves into something: W = F × d, with the distance measured along the force.
Its unit is the joule: 1 J = 1 N·m, a push of 1 N over 1 m.
Machines like ramps trade force for distance. Simplified model: no friction. With friction you do a bit more work than the energy you store.
Lift a piano 1.5 m three ways. Tap each machine.
Game: Pyramid builder. Find the shortest ramp your crew can push the block up.
A ramp that is too steep fails. One that is too long wastes stone. Three levels.
Math: a spring pulls harder the more you stretch it. Which region is the work?
Tap A, B or C, then Check.
A 20 kg crate is lifted 1.5 m onto a shelf. How much work, in joules?
Your ramps from the game. Press Play to build the pyramid.

Lessons are interactive and need JavaScript. Turn it on to play them.