A rock is thrown at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the velocity of the rock at the highest point of its trajectory?

A) 0

B) 9.8 m/s

C) It is equal to its initial horizontal velocity.

D) It is equal to its initial vertical velocity.

E) It is equal to its initial velocity.

A student kicks a soccer ball in a high arc toward the opponent’s goal. At the highest point in its trajectory:

A) both velocity and acceleration of the soccer ball are zero.

B) neither the ball’s velocity nor its acceleration is zero.

C) the ball’s acceleration is zero but not its velocity.

D) the ball’s acceleration points upwards.

E) the ball’s velocity points downwards.

When a football in a field goal attempt reaches its maximum height, how does its speed compare to its initial speed?

A) It is zero.

B) It is less than its initial speed.

C) It is equal to its initial speed.

D) It is greater than its initial speed.

E) Cannot be determined without additional information.

**EXPERT ANSWER**

A rock is thrown at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the velocity of the rock at the highest point of its trajectory?

A) 0

B) 9.8 m/s

C) It is equal to its initial horizontal velocity.

D) It is equal to its initial vertical velocity.

E) It is equal to its initial velocity.

**Answer :**C) It is equal to its initial horizontal velocity.

A student kicks a soccer ball in a high arc toward the opponent’s goal. At the highest point in its trajectory:

A) both velocity and acceleration of the soccer ball are zero.

B) neither the ball’s velocity nor its acceleration is zero.

C) the ball’s acceleration is zero but not its velocity.

D) the ball’s acceleration points upwards.

E) the ball’s velocity points downwards.

**Answer :**B) neither the ball’s velocity nor its acceleration is zero.

When a football in a field goal attempt reaches its maximum height, how does its speed compare to its initial speed?

A) It is zero.

B) It is less than its initial speed.

C) It is equal to its initial speed.

D) It is greater than its initial speed.

E) Cannot be determined without additional information.

**Answer :**B) It is less than its initial speed.

**Answer : **B) decreases.