What it does
Machines do not give you free work, but they let you swap a big force over a short distance for a small force over a long one. This lab has four of them. Pick one, set the load, and the page shows the effort you need, the mechanical advantage (MA = load ÷ effort), the velocity ratio (VR = how far the effort moves ÷ how far the load rises) and the efficiency (MA ÷ VR). Drag sideways on the picture, or move the Pull slider, to work the machine: the load rises while the effort moves, and the work in and work out are added up.
- Lever: choose class 1 (fulcrum in the middle), class 2 (load in the middle) or class 3 (effort in the middle) and move the fulcrum, load or effort along a 2 m beam.
- Pulleys: 1 to 4 strands holding the load, with the weight of the moving pulleys and some friction.
- Ramp: push a load up a slope of any length and height, with friction.
- Wheel and axle: turn a big wheel to wind a rope on a small axle, like a well winch.
It follows the school topics on simple machines, mechanical advantage, velocity ratio and efficiency, alongside work and energy (Class 9 Science, work, energy and simple machines). The energy side is in energy skate track, the forces in newton's laws sandbox and the ramp with friction in friction ramp; for gears, see gear trains.
How to use it
- Choose a machine with the buttons at the top.
- Set the load mass. Its weight in newtons is mass × 9.8.
- Change the machine’s own settings: lever class and position, number of strands, ramp length and height, or wheel and axle sizes.
- Add friction (or lower the efficiency) to see why real machines need more effort than the ideal.
- Drag across the picture or use the Pull slider to move the effort and watch the load rise.
Worked example
Open the page: a class 1 lever with a 60 kg load (588 N) at the end, the fulcrum 0.5 m from the load and the effort at the other end, 1.5 m from the fulcrum. Moments: effort × 1.5 = 588 × 0.5, so the effort is 196 N. MA = 588 ÷ 196 = 3, VR = 1.5 ÷ 0.5 = 3, efficiency 100 % (no friction at the pivot).
Switch to Pulleys with 2 strands, 2 kg of moving pulleys and 5 % friction. The load and pulleys weigh 588 + 19.6 = 607.6 N, shared by two strands: 303.8 N, plus friction gives an effort of 319.8 N. MA = 588 ÷ 319.8 = 1.84, VR = 2, efficiency 91.9 %.
On the Ramp (5 m long, 1 m high, μ 0.1) the effort is 175.2 N instead of lifting 588 N: VR 5, efficiency 67.1 %.
Tips
- MA can never beat VR in a real machine, because some work always goes into friction or lifting the machine’s own parts.
- A class 3 lever has MA below 1, yet it is useful: your hand moves a little and the far end moves a lot, fast.
- More pulley strands means less effort but more rope to pull: four strands, four metres of rope for each metre the load rises.
FAQ
Why is a single fixed pulley useful if MA is 1? It changes the direction of the force: you can pull down, using your own weight, to lift something up.
What is the difference between MA and VR? VR comes from the shape of the machine (distances) and does not change with friction. MA comes from the actual forces, so friction lowers it.
Is anything saved? No. Everything is worked out in your browser.
Where the numbers come from
- The principle of moments, mechanical advantage (load ÷ effort), velocity ratio (effort distance ÷ load distance), efficiency (MA ÷ VR) and the work principle for levers, pulleys, the inclined plane and the wheel and axle: standard school physics found in any textbook. g = 9.8 m/s² (rounded).
- Checked against the principle of moments and the work principle on 500 random machines and against hand-worked examples. The masses and friction values are made-up examples.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.