contestada

A ball is thrown vertically into the air and when it returns after an interval of 2 seconds, it is caught. Which one of the following statements is true if the acceleration due to gravity is 10 m/s/s and air resistance can be neglected?


The acceleration at the top of its flight is 10 m/s/s upwards.

The acceleration at the top of its flight is 0 m/s/s.

The time taken for the descending motion does not equal the time taken for the ascending motion.

The acceleration after it leaves the hand is 10 m/s/s downwards.

Respuesta :

mberisso

Answer:

Last statement option: "The acceleration after it leaves the hand is 10 m/s/s downwards."

Explanation:

At every instant of its motion, the ball is under the effects of the acceleration due to gravity (assumed to be 10 m/s^2). This is true at whatever altitude the ball is. The acceleration due to gravity is always pointing down (not up).

In the absence of air resistance, the motion is described kinematically by a parabola with the branches pointing down as a function of time (motion under constant acceleration), with the vertex indicating the maximum altitude the ball reaches. Both branches (representing motion upwards and downwards) are equidistant from the vertex, so the time going up equals the time coming down.

Therefore, the only statement option that is correct is the last one: "The acceleration after it leaves the hand is 10 m/s/s downwards."

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