A tennis ball is tossed straight up into the air. It flies up, it reaches the peak position, and then it falls back down. What can we tell about the ball's velocity and acceleration, when the ball is at the peak of its trajectory? (Only one answer is correct.)

A. The velocity is zero, and the acceleration points up.
B. The velocity points up, and the acceleration is zero.
C. Both the velocity and the acceleration point up.
D. The velocity points down, and the acceleration is zero.
E. The velocity points down, and the acceleration points up.
F. Both the velocity and the acceleration point down.
G. The velocity is zero, and the acceleration points down

G. The velocity is zero, and the acceleration points down.

Explanation:

When a ball is tossed up with an intial velocity, the motion at that time is againt morion that is, a = -g m/s^2. As soon as this ball gets to its maximum height, the final velocity at that point is 0 and the acceleration points down; a = g m/s^2.

The acceleration of the ball is equal to the gravitational acceleration (-9.8 m/s2) during the entire motion regardless of its position, which means that after the ball is thrown its velocity starts decreasing during the upward motion, it declines to the zero. This change in the sign from positive to negative can only happen when the velocity is equal to zero.

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