# Homework Help: Bullets and Gravity

1. Feb 18, 2006

### Creative

If someone fires a bullet straight up into the sky, how high will it go? Will it return to the earth at the same velocity that it left the gun?

2. Feb 18, 2006

### phucnv87

It depends on the air resistance.
If we ignore the air resistance, the height is $$H=\frac{v_0^2}{2g}$$ and the velocity when it returns the earth is its initial velocity.

Last edited: Feb 18, 2006
3. Feb 18, 2006

### turbo

If you want to study anything but the most simplified approximation, you enter the word of ballistics, and you may never emerge.

4. Feb 18, 2006

### Pengwuino

:rofl: :rofl: :rofl: :rofl: Yah if you want any sort of accurate description of the bullet, you'll basically have a good model until the thing leaves the barrel and then its a free-for-all as to what it's going to do.

Yah when you put a small light object into the air at high altitudes, it's going to get pushed around all over the place by the winds. Of course, air resistance will be slowing it down too.

5. Feb 20, 2006

### ZackQuantum

Wouldn't the maximum velocity of any smaller caliber bullet be lower, even in a world of theoretically perfect fluid mechanics based to give minimal resistance and maximum aid, than the initial speed caused by the explosion?

6. Feb 20, 2006

### R34p3r

yeah

it will go up as high as it can it becomes a projectile you can get those equations just by looking up in wikipedia. but it will come down at the same velocity that it went up at.

7. Feb 20, 2006

### Tide

Well, no it won't. A bullet is launched at a speed greater than the terminal velocity and returns at a speed not exceeding the terminal velocity.

8. Feb 21, 2006

### phucnv87

Without air resistance, what lessenes the speed of the bullet?

9. Feb 21, 2006

### Tide

Nothing, but the scenario described by ZackQuantum to which R34p3r responded includes air resistance. Note the words "minimal resistance" and "theoretically perfect fluid mechanics."

10. Feb 21, 2006

### R34p3r

yeah

sorry bout that my bad i meant if there is no air resistance