Homework Help: Collisions in One Dimension

1. Oct 9, 2011

Joyci116

1. The problem statement, all variables and given/known data
A 10.0g bullet is fired into a stationary block of wood (m=5.00 kg). The bullet imbeds into the block. The speed of the bullet-plus-wood combination immediately after the collision is 0.600 m/s. What was the original speed of the bullet?

ball m=10.0g=0.01kg
wood m= 5.00kg
Vf=0.600m/s
Vi=?

2. Relevant equations
p=mv

3. The attempt at a solution
i=change in momentum
=mVi-mVf
So, solve for Vi?
Then I would have to know what i is, right?

Thank you.

2. Oct 9, 2011

Staff: Mentor

Write equations for the momentum before and after the collision takes place. Be sure to specify which masses are involved.

3. Oct 10, 2011

Joyci116

p=mv
The momentum found using final velocity:
p=(0.01kg)(0.600m/s)=0.006 kg*m/s (ball)
p=(5.00kg)(0.600m/s)=0.006 kg*m/s (wood)
And I assumed the initial velocity was zero, so I ended up with a zero momentum.
Is that correct so far?

4. Oct 10, 2011

lightgrav

no, the bullet started with (fast) unknown velocity
It was theonly thing that HAD momentum, at first.

5. Oct 15, 2011

Joyci116

Thanks, I finally figured it out. :D

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