Question

Suppose that you toss a rock upward so that it rises and then falls back to the earth. If the acceleration due to gravity is 9.8 m/sec2,

what is the rock’s acceleration at the instant that it reaches the top of its trajectory (where its velocity is momentarily zero)?
Assume that air resistance is negligible.

A)The acceleration of the rock is zero.
B)The rock has an upward acceleration of 19.6 m/s2.
C)The rock has a downward acceleration of 19.6 m/s2.
D)The rock has a downward acceleration of 9.8 m/s2.
E)The rock has an upward acceleration of 9.8 m/s2.

Answer 1

At the top of its trajectory, the rock experiences a downward acceleration of 9.8 m/s² due to gravity, regardless of its temporary zero velocity. Option D

Step-by-step explanation:

When a rock is tossed upward and reaches the top of its trajectory, the velocity of the rock is momentarily zero. However, the acceleration due to gravity is a constant force and always acts downward, regardless of the motion of the object.

Therefore, at the top of its trajectory, the rock's acceleration is not zero, nor is it upward. Instead, the rock experiences a downward acceleration of 9.8 m/s², which is the standard acceleration due to gravity near the Earth's surface. Thus, the correct answer is D) The rock has a downward acceleration of 9.8 m/s².

This reflects a key principle in physics: the acceleration due to gravity is constant for any object in free fall, whether it is moving up, down, or at the top of its path where the velocity is zero. Option D

Answer 2

"The rock has a downward acceleration of 9.8 m/s2" is the one among the following choices that explains the rock’s acceleration at the instant that it reaches the top of its trajectory (where its velocity is momentarily zero). The correct option among all the options that are given in the question is option "D".