A disk is free to rotate on a fixed axis.A force of given magnitude F, in the plane of the disk, is to be applied.Of the following alternatives the greatest angular acceleration is obtained if the force is:
A)applied tangentially halfway between the axis and the rim
B)applied tangentially at the rim
C)applied radially halfway between the axis and the rim
D)applied radially at the rim
E)applied at the rim but neither radially nor tangentially

Question

Quizplus · Accepted Answer

The greatest angular acceleration is obtained when the force is applied tangentially at the rim of the disk. This is because the torque due to the force is the greatest when the force is applied at the point farthest from the axis of rotation, which is the rim. The torque is given by τ = Fr, where F is the force applied, and r is the distance between the force and the axis of rotation. Since r is maximum at the rim, the torque and hence the angular acceleration is also maximum at the rim.

A Disk Is Free to Rotate on a Fixed Axis