physics question about kinematics

Question

A ball is thrown into the air from a height of 2.00 m and with an initial velocity of 5.00 m/s at an angle of above the horizontal. Select all of the quantities that are zero at some time (not necessarily the whole time) between when the ball is first thrown and just before the ball hits the ground.

1. The vertical component of the velocity of the ball
2. The horizontal component of the acceleration of the ball
3. The vertical component of the acceleration of the ball
4. The magnitude of the momentum of the ball
5. The horizontal component of the velocity of the ball



Answer 1

The ball starts with non-zero horizontal velocity, and

with non-zero vertical velocity oriented upward.

After the ball is thrown, it it subject to only one force -- gravity.

That force causes constant downward gravitational acceleration.

Therefore the ball experiences constant non-zero vertical acceleration, and

constant zero horizontal acceleration.

Vertical acceleration is constant non-zero, therefore option 3. is not correct.

Horizontal acceleration is constant zero, therefore option 2. is correct.

Vertical acceleration is constant non-zero, and downward, therefore vertical velocity

becomes more and more downward.

Since vertical velocity starts as upward, it is decreasing until it becomes 0.

Thereafter it become bigger and bigger downward.

Therefore option 1. is correct.

Horizontal acceleration is constant zero, therefore horizontal velocity is constant.

Initial horizontal velocity is non-zero, therefore horizontal velocity remains the same non-zero,

therefore option 5 is not correct.

Horizontal velocity remains non-zero, therefore overall velocity is also non-zero,

therefore momentum is also non-zero.

Therefore option 4. is not correct.