Levers, gears and torque
Before you start
A door is easier to turn farther from its hinge: position and direction matter as well as force.
The setupLever: a fixed pivot supports a load on the right and a slowly controlled effort on the left. Gears: a motor turns the gold input gear, while a matched resisting load keeps the blue output turning steadily.
What to do and noticeWhy is the same force more effective farther from the pivot? · Does a longer effort arm always help? · Why does the larger output turn slower but transmit more torque?
Predict firstWhy is the same force more effective farther from the pivot?
A door is easier to turn farther from its hinge: position and direction matter as well as force.
Prerequisites: Lever: a fixed pivot supports a load on the right and a slowly controlled effort on the left. Gears: a motor turns the gold input gear, while a matched resisting load keeps the blue output turning steadily.What torque measures
Predict firstWhy is the same force more effective farther from the pivot?
Torque measures how a force tends to change rotation about a specified axis. Its magnitude is τ = Fd = rF sinα. The moment arm d is the perpendicular distance from the axis to the force line, not necessarily the rod length. Red marks the applied force and gold marks d. Move inward: the required balancing force rises. A force line through the axis has d = 0 and no torque about that axis.
How to observe
- Why is the same force more effective farther from the pivot?
- Does a longer effort arm always help?
- Why does the larger output turn slower but transmit more torque?
Model notes
Rigid frictionless apparatus. Lever motion is a slow imposed sweep displaying the balancing force, not an unbalanced dynamic simulation. External involute gears neglect backlash, deformation and inertia. A matched load balances motor torque at prescribed speed.