# Homework Help: Impulse Question

1. Jan 20, 2009

### acsin92

1. The problem statement, all variables and given/known data

A bullet with a mass of 0.005 kg and moving with a speed of 400 m/s penetrates a distance of 0.08m into a wooden block firmly attached to the Earth. Assume that the force stops it is constant. Compute for:

a.) acceleration of the bullet
b.) accelerating force
c.) time of acceleration
d.) impulse of the bullet

2. Relevant equations

I think I'll use

a=-Vi^2 / 2s.

for the acceleration of the bullet.

then for the acceleration of the bullet,

F=m(Vf-Vi)

then for the time of acceleration,

t = m(Vf-Vi) / F

am i right?

2. Jan 20, 2009

### PhanthomJay

yes
No, what is Newton's second law?
yes, (or use t = (Vf -Vi)/a , as a check)
and part d?

3. Jan 21, 2009

### acsin92

a.) acceleration of the bullet = 1,000,000 m/s^2
b.) accelerating force = 5000N
c.) time of acceleration = 0.0004 s
d.) impulse of the bullet = 2 Ns

are these correct? I used the equations above. I'm in doubt whether this is correct because of those large numbers and for that small amount of time.

I used the equation of I=Ft for impulse.

Last edited: Jan 21, 2009