Posted by **JC** on Sunday, September 10, 2006 at 2:09pm.

A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun straight down towards the water.

If air resistance is negligible, the acceleration of the bullets just before they strike the water

A. is greater for the dropped bullet.

B. is greater for the fired bullet.

C. is the same for both bullets.

D. depends on how high they started.

I really should let the physics gurus handle this, but I see they haven't yet. I also see you've posted a lot of questions with no attempt at answers. You aren't expecting us to do your homework are you?

If air resistance is negligible then the formula for a falling object is

s(t)=(-1/2)gt^2+v_0t+s_0

where v_0 is the initial velocity and s_0 is the initial height.

From this we get the velocity of the object at time t

v(t)=-g*t+v_0

For the dropped bullet v_0 is 0

For the fired bullet v_0 is negative.

The question however is concerned with the acceleration. We then get the acceleration as

a(t)=-g

This applies to both objects.

Here's what we can say about the answers:

A. The dropped bullet as 0 initial velocity, but is being upon by gravity.

B. The fired bullet has greater initial velocity, but is being acted upon by gravity.

C. What do you think?

D. Does the height affect the acceleration?

C

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