When a projectile is fired at 45 deg. angle and is in free fall, the only point along the path that the acceleration of the object is zero is the instant when the object is at the highest point of its path.

Question

Answer: False
Can someone explain how?

2.) An object with acceleration in the positive x-direction (to the right) must be moving to the right.
False: Why?

4.) An object starting from ground level that is projected with the initial velocity at a 45 deg. angle upward will have the exact same velocity right before it hits the ground some time later.
FALSE
Explanation please?

6.) If an objects velocity over a given time period is zero, then the object was at rest for that time period.
FALSE
Explanation please?

Answer 1

When a projectile is fired at 45 deg. angle and is in free fall, the only point along the path that the acceleration of the object is zero is the instant when the object is at the highest point of its path.
Answer: False
Can someone explain how?
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F = m a
the force is constant = m g
so the whole time the acceleration is 9.81 m/s^2 down
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2.) An object with acceleration in the positive x-direction (to the right) must be moving to the right.
False: Why?
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If you are going left, negative x speed at 10 m/s
and put the brakes on.
Your acceleration is + to the right
F = m a again :)
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4.) An object starting from ground level that is projected with the initial velocity at a 45 deg. angle upward will have the exact same velocity right before it hits the ground some time later.
FALSE
Explanation please?
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Due to symmetry it will have the same SPEED
BUT
NOT the same velocity vector because the vertical component of velocity is now DOWN
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6.) If an objects velocity over a given time period is zero, then the object was at rest for that time period.
FALSE
Explanation please?
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True as far as I know. If it is not moving it is at rest.
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