A block is at rest on a frictionless horizontal plane. As one end of the plane is slowly raised, the block eventually "breaks loose" when the plane makes an angle $\theta$ , with the horizontal. The coefficient of kinetic friction can be calculated by assuming
A) constant displacement of the block.
B) constant speed of the block.
C) constant acceleration of the block.
D) none of the above.

Question

Quizplus · Accepted Answer

When the block "breaks loose" and starts moving down the inclined plane, it does so with constant speed if the plane is frictionless or if the kinetic friction force exactly balances the component of gravitational force parallel to the plane. This implies that the net force on the block is zero, leading to a state of dynamic equilibrium where acceleration is zero. Therefore, the coefficient of kinetic friction can be calculated under the assumption of constant speed, as this reflects the condition under which the forces are balanced.

A Block Is at Rest on a Frictionless Horizontal Plane θ\thetaθ

A Block Is at Rest on a Frictionless Horizontal Plane $\theta$