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

A car is driving along on a flat horizontal road at $35\mathrm{m}/\mathrm{s}$ when the driver quickly slams on the brakes and comes to a stop. The coefficient of kinetic friction between the tires and the road is $0.810$.

Which of the following values is the distance the car travels before coming to a complete stop?

An object of mass $7.5\mathrm{kg}$ is being pulled at a constant speed up an inclined plane at an angle of $35°$ to the horizontal by a force of $55\mathrm{N}$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 $m$ is at rest on an inclined plane. The coefficient of static friction between the object and the surface of the plane is $0.71$.

Which of the following is the largest angle of incline of the plane before the object starts to slip?

Children of different masses are taking it in turns to sit in a sledge and slide down a steep incline of $60°$ to the horizontal. The maximum static frictional force applied to the sledge and the children before it begins to move is $450\mathrm{N}$. 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?

A horizontal force $F$ is applied to a $7.5\mathrm{kg}$ box which remains at rest on a rough horizontal surface with ${\mu }_s=0.4$.

Which of the following most nearly gives the maximum force that can be applied without moving the box?

A $6.0\mathrm{kg}$ block slides down a $5.0\mathrm{m}$ incline at an angle of $35°$ to the horizontal. The coefficient of kinetic friction is ${\mu }_k=0.25$. The block starts to move from rest at the top of the incline.

Which of the following most nearly gives the speed of the block at the bottom at the incline?

A solid disk of mass $4.0\mathrm{kg}$ and radius $0.6\mathrm{m}$ rolls without slipping down a $3.0\mathrm{m}$ incline angled at $25°$. The coefficient of static friction is ${\mu }_s=0.3$.

The acceleration of a solid disk is given by the equation $a=\frac{2}{3}g\sin \theta$

Which of the following gives the frictional force acting on the disk?

A $5.0\mathrm{kg}$ block is placed on a rough inclined plane with an angle $\theta =30°$. The coefficients of static and kinetic friction are ${\mu }_s=0.4$ and ${\mu }_k=0.3$ respectively.

Which of the following most nearly gives the ratio of the acceleration of this block to a block with triple the mass as it slides down the incline?

A $3.0\mathrm{kg}$ block slides on a horizontal surface with an initial velocity of $15.0\mathrm{m}/\mathrm{s}$. The coefficient of friction is ${\mu }_k=0.25$.

Which of the following gives the distance the block travels before coming to rest?

A $15.0\mathrm{kg}$ box is pushed horizontally with a force $F=50.0\mathrm{N}$ on a rough horizontal surface. It does not move due to the static friction it experiences where ${\mu }_s=0.5$. If the box were to move then ${\mu }_k=0.3$.

Which of the following most nearly gives the fraction $\frac{\left|{\overrightarrow{F}}_s\right|}{\left|{\overrightarrow{F}}_k\right|}$ the box were to experience if it does move?