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Torque
Point at which all other points on the object rotate around
During motion the CM will move in the same path that a simple particle would move if subjected by the same force
Objects supported at their center of mass will remain balanced
Center of Mass or Center of Gravity (CM or CG)
In order to make an object start rotating about an axis, a force is required
However, not only the amount of force applied but also the position from the axis to which it is applied is important in determining the amount of rotation (angular acceleration
Distance from axis is called the Lever Arm
Causing Rotational Motion
A longer lever arm is very helpful in rotating objects.
© 2014 Pearson Education, Inc.
Combination of amount of force and distance from axis is called Torque (τ)
A torque is necessary in order to provide angular acceleration
τ = rF r- dist from axis Units - N m In order to use this equation, the force must
be perpendicular to the axis of rotation
Torque Definition
A biceps muscle exerts a vertical force on the lower arm as shown. Calculate the torque acting on the lower arm if the muscle is attached 5.0 cm from the elbow.
Example 1
A wrench is pulled by a force of 30 N at an angle of 30° with the axis and a distance of 15cm from its pivot end. What torque is acting on it?
Example 2
Two forces (FB = 20N and FA = 30N) are applied to a meterstick which can rotate about its left end. FB is applied perpendicular at the midpoint. FA is exerted at the endpoint at an angle of 30o. Which exerts the greater force?
Example 3
