# Homework Help: Need help going over a momentum/spring problem

1. Jun 21, 2009

### groundhog92

1.The problem statement, all variables and given/known data
A pellet gun is fired into a block of wood that is attached to a spring on a frictionless surface. The bullet remains in the wood and the block of wood and the bullet enter into a simple harmonic motion with Amplitude=11cm. The 5g bullet was traveling at 650m/s before hitting the 2.5kg block of wood.
a)What is the spring constant?
b)What is the the total energy of the system after the collision?
c)What is the max acceleration of the bullet/block once it begins its oscillation?
d)Where will the bullet/block reach a velocity of 0?

2. Relevant equations
mv=mv
(1/2)mv^2=(1/2)kx^2
a=(V^2)/A
v=2pief(sqrt(A^2-x^2))

3. The attempt at a solution
I've already done the problem I just need someone to check my work because I'm not completely sure about the process.

Part a
(.005)(650)=(2.505)v
v=1.3m/s

(1/2)k(.11^2)=(1/2)(2.505)(1.3^2)
k=349.9N/m

Part b
E=(1/2)mv^2 + (1/2)kx^2
E=((2.505)(1.3^2)+(349.9)(.11^2))/2
E=4.23J

Part c
a=(v^2)/A
a=(1.3^2)/.11
a=15.4m/s^2

Part d
Where A=x
so where x=+-11cm

Thanks in advance for any help.

2. Jun 21, 2009

### davieddy

In part b) you have added the max KE to the max PE.
When KE is max, PE is zero and vice versa.

3. Jun 21, 2009

### groundhog92

So the total energy of the system would be equal to just the max potential or kinetic by themselves?

4. Jun 21, 2009

### davieddy

Yep!

5. Jun 21, 2009

### groundhog92

alright thanks