本题目来源于试卷: Space Time & Motion A.1 Kinematics，类别为 IB物理学
[单选题]
The graph shows the iu aofliufj m)y8z,8u4+j.2 d-h 8 lwjvariation ofe9el 60k3qnl t velocity v of a ball with time t.
The initial speed of the ball is very high. Which of the following statements could be true for the ball?
A. It is thrown vertically upward in the presence of air resistance.
B. It is thrown vertically upward in the absence of air resistance.
C. It is thrown vertically downward in the presence of air resistance.
D. It is thrown vertically downward in the absence of air resistance.
参考答案: C
本题详细解析:
Explanation: According to the graph, the ball has a decreasing deceleration and reaches terminal velocity. Since the acceleration of the ball is not constant, air resistance must be acting on the ball. Air resistance always acts in the direction opposite to the velocity. In an upward motion, air friction and gravity are in the same direction. Therefore, it is not possible for them to cancel each other so that the ball reaches terminal velocity. It should be moving in the downward direction. Hence, the answer is C.
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