Kinetic and Static Friction AP Physics 1 MCQ – Exam Style Questions etc.
Kinetic and Static Friction AP Physics 1 MCQ
Unit: 2. Force and Translational Dynamics
Weightage : 10-15%
Exam Style Practice Questions, Kinetic and Static Friction AP Physics 1 MCQ
Question
A block of mass m is initially moving on a rough horizontal surface as shown in Figure 1. Figure 2 shows the four forces acting on the block. Which of the following best describes the motion of the block at the moment shown in the two figures?
A The block is moving to the right and speeding up.
B The block is moving to the right at a constant speed.
C The block is moving to the right and slowing down.
D The block is moving to the left at a constant speed.
E The block is moving to the left and slowing down.
Answer/Explanation
Ans:C
The velocity vector is to the right, indicating that the block is moving to the right. For the forces, the vector to the left is larger than the vector to the right, indicating that the net force and the resulting acceleration are to the left. An object moving to the right with an acceleration to the left is slowing down.Question
Two blocks rest on a table, as shown above. The bottom block is pulled to the right by an applied force \(\vec{F}\) F that is strong enough so that the two blocks do not move together (i.e., they do not have the same acceleration or velocity). There is friction between the blocks, but the tabletop is frictionless. When the top block leaves the bottom block, where does it land and why?
(A) The top block will land directly below where it starts because objects at rest tend to stay at rest.
(B) The top block will land to the left of where it starts because of the static friction between the blocks.
(C) The top block will land to the left of where it starts because of the kinetic friction between the blocks.
(D) The top block will land to the right of where it starts because of the static friction between the blocks.
(E) The top block will land to the right of where it starts because of the kinetic friction between the blocks.
Answer/Explanation
Ans:E
The top block accelerates to the right, but does not move as fast as the bottom block. The force exerted on the top block is friction from the bottom block. Since the blocks do not move together, the friction is kinetic friction. Since the blocks are moving toward the right, the top block will land to the right of where it started.