Solve Impulse Question on Bullet Acceleration & Force

[acsin92]

Homework Statement

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

Homework 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?

 

[PhanthomJay]

Homework Statement

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

Homework Equations

I think I'll use

a=-Vi^2 / 2s.
for the acceleration of the bullet.

yes

then for the accelerating force [/color]of the bullet,

F=m(Vf-Vi)

No, what is Newton's second law?

then for the time of acceleration,

t = m(Vf-Vi) / F

yes, (or use t = (Vf -Vi)/a , as a check)

am i right?

and part d?

 

[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.