Question

A ball is thrown straight up in the air. For which situation are both the instantaneous velocity and the acceleration zero?
A. on the way up
B. at the top of its flight path
C. on the way down
D. halfway up and halfway down
E. none of the above

Answer 1

Hint:Acceleration is defined as the rate of change of velocity of an object with respect to time. An object moving towards or against the gravity of the earth moves under the acceleration of the earth’s gravity. Instantaneous velocity is the velocity of an object at a very particular point in time.

Complete answer:
When a ball is thrown straight up in the air, it moves against gravity and in that condition, the acceleration acting on it is $$-g$$. The velocity of that ball changes at every point and decreases to zero as it reaches the top then again the velocity increases as the ball goes down. Through the whole episode, the acceleration remains the same, i.e. $$-g$$. The instantaneous velocity can be zero at the highest point but not the acceleration. All options from A to D are incorrect.

Hence, the correct answer is E.

Note: The acceleration of any object moving under the influence of gravity is called acceleration due to gravity. This quantity called the acceleration of gravity is so important that physicists have a special symbol, which is represented by the symbol g. The value of the acceleration due to gravity is most accurately known as $9.8m/s^2$. This value shows a slight deviation (up to the second decimal place), mainly depending on the height.