Torque

Rotational Motion

Torque

Forces that cause objects to rotate

Two Characteristics that contribute to the effectiveness of torque: Magnitude of force

Increase force – increase torque- increase angular acceleration (F = ma)

Where the force is applied

Example: Opening a Door

Not all of the forces will create a torque and cause the door to rotate. Which force will create a torque?

Formula for Torque

Torque = (sinθr)F

Torque - Lever arm – r (m) Force – F (N) Angle – θ

Unit for Torque is Nm

Net Torque and Direction

Net Torque - sum of all torque acting on one object

Direction – If the force causes clock-wise rotation,

the Torque is negative If the force causes counterclockwise

rotation, the Torque is positive

Sample problem

Calculate torque for all forces (add angles and distances)

Sample problem #1

If pulley radius = 5 cm find torque

Sample Problem #2

F1 = 10N, F2 = 15 N

what is net torque

Sample Problem #3

Find Net Torque