# Conceptual question

I'm really bad at these because there are multiple answers and I always leave one out. :grumpy:

A projectile is fired from a ship at a distant, floating target. Which of the following statements are true? (There can be more than one correct choice.)

a. The vertical component of the projectile's acceleration does not change with time.
b. The speed of the projectile does not change with time.
c. The vertical component of the projectile's velocity does not change with time.
d. The horizontal component of the projectile's acceleration does not change with time.
E. The horizontal component of the projectile's velocity does not change with time.

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Galileo
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There is only one force acting on the projectile. Gravity gives the projectile a vertical acceleration downwards. What effect does this have on the speed and acceleration components of the projectile?

I know that B is incorrect because the speed is slowing down due to gravity. C is also incorrect because the velocity varies when the projectile moves in a parabola. D is incorrect because there is no horizontal component in the acceleration. A is correct because the vertical acceleration is constant due to gravity. So what I can't decide is if E is correct or not. I'm thinking no because the velocity will change once the projectile hits its target. Am I on the right track?

Galileo
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xelda said:
D is incorrect because there is no horizontal component in the acceleration.
Think about that one. If the horizontal acceleration is zero, does it change with time?

A is correct because the vertical acceleration is constant due to gravity. So what I can't decide is if E is correct or not. I'm thinking no because the velocity will change once the projectile hits its target. Am I on the right track?
E is related to D. If there is no horizontal acceleration. What does it mean for the horizontal velocity.

Oh, and I think you should only consider these question when the projectile is flying, not including the impact on the target. Galileo said:
Think about that one. If the horizontal acceleration is zero, does it change with time?
Shoot! I didn't consider that. Thank you so much for your help!