Unequal Lever: Mechanical Advantage
1 · Predict
This lever's pivot is centered, just like the classic lever — but the right force is applied only 1 m from the pivot while the left force is 2 m away. If a 50 N push at the 2 m distance is balanced by a push at the 1 m distance, is that force bigger, the same, or smaller than 50 N?
- It is bigger than 50 N
- It is the same — 50 N
- It is smaller than 50 N
2 · Set Up
- Open the Unequal Lever preset. A rigid beam is pinned at its exact center, like the classic lever — but the two downward forces are applied at different distances: 2 m on the left, 1 m on the right. A 50 N downward force pushes at the 2 m mark.
- Click the left force arrow on the beam and note its strength in the Inspector, then click the right force arrow and do the same. Notice the two arms are different lengths.
- For each row below, set the left and right force strengths in the Inspector to match, run the simulation, select the beam, and read the τ = r × F torque value from the Math panel.
3 · Collect Data
| Left Force (N) | Right Force (N) | Net Torque (from sim) (N·m) | τ = r × F (calculated) (N·m) |
|---|---|---|---|
| 50 | 100 | ||
| 50 | 50 | ||
| 20 | 100 |
Plot the force difference (Right Force − Left Force) on the x-axis against the net torque you measured on the y-axis — remember the arms are unequal, so the torque is 1 m × Right Force − 2 m × Left Force. What does the slope represent, and where does the line cross zero?
4 · Analyze
- For each row, calculate 1 m × Right Force − 2 m × Left Force by hand. Compare it to the net torque you read from the sim's Math panel. Do they match?
- In row 1 the 50 N push on the 2 m arm balances the 100 N push on the 1 m arm — different forces, equal torques. What must be true of a force and its distance from the pivot for a lever to balance?
5 · Extend
- A wheelbarrow is a lever too: your arms lift the handles about 2 m from the wheel (the pivot) while the load sits close to the wheel. If the load weighs 200 N and sits 0.5 m from the wheel, what upward force must you apply at the handles to balance it? What would you need if the load sat at the very end of the tray?
- A claw hammer pulling a nail, a crowbar, and a nutcracker are all levers with unequal arms. Pick one and identify its pivot, its applied force, and the load it moves — then explain why the short arm is the one on the load side.
The Physics Behind This Experiment
Torque
Torque is the turning effect of a force about a pivot: τ = r × F, where r is the distance from the pivot to where the force acts. With unequal arms, equal torques need unequal forces — a 50 N force 2 m from the pivot balances a 100 N force 1 m away, because both make 100 N·m.