What Force Does the Wood Exert on the Bullet?

[mrnastytime]

Homework Statement

A bullet of mass 0.002 kg initially moving at 510 m/s embeds itself in a large fixed piece of wood and travels 0.78 m before coming to rest. Assume that the acceleration of the bullet is constant.

Homework Equations

What force is exerted by the wood on the bullet?

The Attempt at a Solution

In order to find the force, I had to solve for acceleration using the velocity vs function equation: v^2=V0^2 + 2a\Deltax
a=v^2-V0^2/2\Deltax
a=0-(510)^2/2(.78)
I plugged in the numbers to the equation f=ma, but it doesn't work. Can anybody help me?

 

[nvn]

It seems to work fine using the equations you posted, which seem correct. Can you show your work, and explain what you mean by the statement, "It doesn't work"?

 

[mrnastytime]

a=0-(510)^2/2(.78)
a=-166730.76
f=0.002kg * -166730 m/s^2
f=-333.46

I entered this answer into my homework online and it is incorrect

 

[nvn]

Nice work; your answer is correct. Should you include units when you enter an answer into your homework on-line? If so, add capital N, for Newtons. If that fails, try removing the negative sign (even though the negative sign is correct). If that fails, try entering your answer to only three significant digits, instead of five. If that fails, the on-line program might be wrong or malfunctioning.

 

[mrnastytime]

Thanks! the answer is 333 N