AP Physics C Mechanics Newton’s First Law MCQ

Newton’s First Law Diagrams AP  Physics C Mechanics MCQ – Exam Style Questions etc.

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Newton’s First Law AP  Physics C Mechanics MCQ

Unit 2: Force and Translational Dynamics

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AP Physics C Mechanics Exam Style Questions – All Topics

Question

Blocks X and Y of masses 3.0 kg and 5.0 kg, respectively, are connected by a light string and are both on a level horizontal surface of negligible friction. A force F = 12 N is exerted on block Y, as shown in the figure above. What is the tension in the string connecting the two blocks?
(A) 1.5 N
(B) 4.0 N
(C) 4.5 N
(D) 7.5 N
(E) 12 N

Answer/Explanation

Ans:C

Question

A sphere of mass m is dropped from the top of a building and reaches the ground before achieving terminal velocity. The force of air resistance that acts on the sphere as it falls is given by  \(F = −kv\) , where k is a positive constant and v is the velocity of the sphere. What happens to the magnitude of the sphere’s velocity and acceleration, and to the distance it falls during each second, as the sphere approaches the ground?
Magnitude of Velocity             Magnitude of Acceleration                                                Distance of Fall Each Second
(A) Increases                                                     Increases                                                                                            Increases
(B) Increases                                                    Decreases                                                                                               Increases
(C) Increases                                                   Decreases                                                                                                Decreases
(D) Decreases                                                 Increases                                                                                                  Decreases
(E) Decreases                                                 Decreases                                                                                                   Increases

Answer/Explanation

Ans:B  

If the sphere never reaches terminal velocity, the resistive force will always be less than the force of gravity; thus, the net force and the acceleration will always be downward. Therefore, the magnitude of the sphere’s velocity will always be increasing. If the magnitude of the sphere’s velocity is always increasing, the distance fallen each second will be increasing. Also, if the sphere is speeding up, the resistive force increases, and the net force and acceleration decrease as the stone gets closer to the ground.

Question

 Two blocks are joined by a light string that passes over the pulley shown above, which has radius R and moment of inertia I about its center. T1 and T2 are the tensions in the string on either side of the pulley and a is the angular acceleration of the pulley. Which of the following equations best describes the pulley’s rotational motion during the time the blocks accelerate?

(A) \(m_2gR = Ia\)

(B) \((T_1+T_2)R = la\)
 
(C) \(T_2R = Ia\)
 
(D)\( (T_2 – T_1)R = la\)
 

(E) \((m_2-m_1)gR = Ia\)

Answer/Explanation

Ans:D

Question

 Two blocks of masses M and m, with M>m, are connected by a light string. The string passes over a frictionless pulley of negligible mass so that the blocks hang vertically. The blocks are then released from rest. What is the acceleration of the block of mass M?

(A)\(g\)

(B)\(\frac{M-m}{M}\)

(C)\(\frac{M+m}{M}\)

(D)\(\frac{M+m}{M-m}g\)

(E)\(\frac{M-m}{M+m}g\)

Answer/Explanation

Ans:E

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