I keep getting “Torque” questions wrong in Rotational Motion. What's the trap?
using the force alone instead of force times perpendicular (lever-arm) distance.
The usual trap: using the force alone instead of force times perpendicular (lever-arm) distance. How to avoid it: pushing a door far from the hinge needs less force — bigger lever arm. Go back to the definition — the turning effect of a force, τ = r×F = rF·sinθ — the rotational analogue of force.
Key point
Torque
Common mistake
using the force alone instead of force times perpendicular (lever-arm) distance.
Memory tip
pushing a door far from the hinge needs less force — bigger lever arm.
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