Kinetic & Static Friction (College Board AP® Physics 1: Algebra-Based)

An object of mass is being pulled at a constant speed up an inclined plane at an angle of to the horizontal by a force of acting parallel to the plane.

Which of the following is the coefficient of kinetic friction between the plane and the object?

An object of mass is at rest on an inclined plane. The coefficient of static friction between the object and the surface of the plane is . Which of the following is the largest angle of incline of the plane before the object starts to slip?

A box of mass is at rest on a wooden floor. The coefficient of friction between the box and the wooden floor is . A force of is applied to the box so it is just at the point of moving.

Which of the following is the maximum magnitude of the static frictional force between the box and the floor?

Children of different masses are taking it in turns to sit in a sledge and slide down a steep incline of to the horizontal. The maximum static frictional force applied to the sledge and the children before it begins to move is . The mass of the sledge is negligible.

Which of the following is a best estimate for the minimum mass of a child that can sit in the sledge and slide down the incline without needing an applied force to get them in motion?