Mechanics
Equal Lever
Two equal forces push down on both ends. Equal arms + equal forces → torques cancel (τ = r × F) → the lever stays level. Change one force in the Properties panel to see it tip.
Lever — interactive Mechanics simulation. Two equal forces push down on both ends. Equal arms + equal forces → torques cancel (τ = r × F) → the lever stays level. Change one force in the Properties panel to see it tip.
Torque and levers
A lever rotates when net torque is nonzero. Forces farther from the pivot produce larger torques for the same magnitude.
Torque τ = r × F depends on both force and lever arm. Equal forces at equal distances on opposite sides can balance; changing distance or force tips the lever.
- τ = rF sin θ
- Στ = 0 at equilibrium
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A lever is pinned at its exact center, with a downward push applied at each end, the same distance from the pivot. If one side pushes harder than the other, does the lever tip toward the stronger push, toward the weaker push, or stay balanced no matter what?
Predictions to weigh
- It tips toward the stronger push
- It stays balanced no matter the forces
- It tips toward the weaker push
Variable roles
What you set:
- Left Force (N)
- Right Force (N)
What you measure:
- Net Torque (from sim) (N·m)
- τ = r × F (calculated) (N·m)
How the investigation runs
- Open the Lever preset. A rigid beam is pinned at its center; a 50 N downward force is applied 2 m from the pivot on each end.
- Click the left force arrow on the beam and note its strength in the Properties panel, then click the right force arrow and do the same.
- For each row below, set the left and right force strengths in the Properties panel to match, run the simulation, select the beam, and read the τ = r × F torque value from the Math panel.
Governing equation
Torque — τ = r × F
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. A lever balances when the torques from both sides cancel — equal forces at equal distances, or unequal forces at inversely proportional distances.
What the printable worksheet asks students to work out
- For each row, calculate 2 m × (Right Force − 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 two forces are equal and the lever stays level. What does that tell you about how forces and arm lengths must relate for any lever to balance?
Where this shows up beyond the lab
- Real levers — like a seesaw with two riders of different weight — often need unequal arm lengths, not unequal forces, to balance. If the right side's force stayed at 50 N but its distance from the pivot doubled to 4 m, what force on the left arm (still at 2 m) would be needed to balance it?
- A wrench, a bottle opener, and a pair of scissors are all levers. Pick one and identify its pivot, its applied force, and the load it moves — then explain why a longer handle makes it easier to use.
- AP Physics 1 — Unit 5: Torque and Rotational Dynamics
- AP Physics C: Mechanics — Unit 5: Torque and Rotational Dynamics
- IB Physics — A.4 Rigid body mechanics
- General High School Physics — Rotation, gravitation & orbits
- NGSS High School Physics — Forces and Newton's second law
- Welcome to Lever
- Select the lever
- Press Play
- Balancing torques
- Open the data
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.