A machine trades force for distance
A 600 N barrel must reach a platform 2 m high. What can you do besides lifting it straight up?
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Step 1 of 4
- A steep ramp needs 600 N over a 2 m push.
- A medium ramp needs 200 N over a 6 m push.
- A gentle ramp needs 75 N over a 16 m push.
- Same load, same rise, less force.
Rule
Push it up a ramp. You use less force, but you push over a longer distance.
A simple machine changes the size or direction of the force. It does not reduce the work. Advantage is short for mechanical advantage. Advantage = load ÷ effort.
- Effort — the force you apply.
- Load — the force you must overcome.
- Mechanical advantage — load ÷ effort.
Think of a ramp with no friction. The push does work effort × length. The lift needs work load × height. With no friction these are equal. Then effort × length = load × height.
Divide both sides by effort × height. Then load ÷ effort = length ÷ height. So the advantage is length ÷ height.
A ramp is 8 m long and 2 m high. Advantage = 8 ÷ 2 = 4. A 600 N load needs 600 ÷ 4 = 150 N.