大学物理英文试题

University Physics AI No. 3 Newton’s Laws of Motion

Class Number Name I．Choose the Correct Answer

1. Which statement is most correct? ( C ) (A) Uniform circular motion causes a constant force toward the center.

(B) Uniform circular motion is caused by a constant force toward the center.

(C) Uniform circular motion is caused by a constant magnitude net force toward the center. (D) Uniform circular motion is caused by a constant magnitude net force away the center.

Solution: For uniform circular motion, the speed or the angular speed of the particle is a constant.

v2

=mω2r, According to Fc=mac=mr

the magnitude of the force toward the center should be constant.

r

2. Suppose the net force F on an object is a nonzero constant. Which of the following could also

be constant? ( D ) (A) Position. (B) Speed. (C) Velocity. (D) Acceleration.

rr

Solution: According to Newton’s second lawF=ma, the answer is (D).

3. Which of the graph in Figure 1 best shows the velocity-time graph for an object launched vertically into the air when air resistance is given by D=bv? The dashed line shows the velocity graph if there was no air resistance. ( B )

t

air resistance is larger than that no air resistance, it implies that the tangent of the graph should be larger than that no air resistance. Thus we remove the answer (D).

During the course of the object moves down, when t→∞, a→0, v→constant. Thinking about this, the right answer is (B)

II. Filling the Blanks