You throw a ball straight up in the air. At the highest point, the ball’s
A) velocity and acceleration are zero
B) velocity is nonzero but its acceleration is zero.
C) acceleration is nonzero, but its velocity is zero.
D) velocity and acceleration are both nonzero.
Solution:
C. The ball reaches its highest point when its velocity is zero. If the velocity is positive, then it is still moving up and will get higher. If the velocity is negative, then it is moving down and was higher at a point in the past.
The acceleration due to gravity will be a constant, g, directed down.
It is possible at an instant in time to both have a nonzero acceleration and not be moving. Thinking about this graphically, the velocity graph is a straight line starting with a positive value and having a negative slope. The point at which the line passes through the axis is the turnaround point.