# Can you confirm the answers?

## Homework Statement

A baseball pitcher throws a fast-ball (mass 50g) to stop a bullet (mass 5g), which has been shot at him at a speed of 400m/s by an angry fan. Can the pitcher save himself by stopping the bullet with a fast-ball of 100mph assuming a perfectly inelastic head-on collision, where the bullet gets stuck in the baseball?

What is the final momentum and the final speed of the baseball+bullet system?

P = mv+mv

## The Attempt at a Solution

So I did:

Final momentum:

P= bullet = (400m/s)(0.005kg) = 2

p = fast-ball = 100mph = 44.7m/s = (44.7m/s)(0.05kg) = 2.235

Pf = 2.235 + 2 = 4.235kg.m/s

Final velocity:

If the question were find the final velocity of the bullet, I guess I´d have written 0, right (because it´s perfectly inelastic)?

But since I am being asked the final speed for both baseball +bullet system, I am attempting:

v = p/m
v = 4.235kg.m/s divided by 0.055kg (total mass) = 77m/s.

So, is that correct?

## The Attempt at a Solution

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You are right all the way up to the point where you get your Pf. That is incorrect, as the momentum is in opposite directions. You should subtract, not add.

So,

pf = 0.235kg. m/s

vf = v/m = 0.235kg. m/s divided by 0.055kg (total mass) = 4.27m/s.

Is that correct now?

Yes. So what can we conclude from your answers? The pitcher can indeed save himself from the bullet. Don't try this at home though, it's a crazy physics question :P.

hahaha!! Thank you SO MUCH!! You are great !!! =)

Np, glad I could help :)