[单选题]
An object is moving in a straight line. The graph shows the variation of the velocity v of the object with time t.
Which of the following is correct according to the graph?
I. At point A, the object changes its direction
II. At point C the object is at rest.
III. The magnitude of the acceleration at point D is greater than at point B.
A. $I$ only
B. $II$ only
C. $I$ and $II$ only
D. $II$ and $III$ only
参考答案:
B
本题详细解析:
Explanation:
The slope of the velocity time graph gives the acceleration of the object. Therefore, at points A and D, there is no acceleration due to zero gradient. At point B, there is a negative acceleration.
Additionally, the velocity of the object at point C is as it aligns with the horizontal axis where v=0.
Hence, the answer is B.
