Calculating Average Force of Bullet Impact on Block

[Freaker]

Homework Statement

A bullet, having a mass of 18g and traveling with a velocity of 1200 m/s strikies a wooden block and pentrates 2.5m. What is the average force exerted by the block on the bullet?

Homework Equations

W= F*total distance
W= .5*m*V2^2 - .5*m*V1^2

The Attempt at a Solution

i got the answer -12960 J

 

[rock.freak667]

i got the answer -12960 J

The question is

What is the average force exerted by the block on the bullet

Now your answer is in Joules..Force is in Newtons...so you missed something

Consider the law of conservation of energy;
The Kinetic energy lost by the bullet= Work done in moving the bullet 2.5m into the wooden block...
$$E_k=W$$

now you know $E_k=\frac{1}{2}mv^2$ and you know $W=Fs$
so you can find F

 

[Freaker]

em i still don't think i have the right answer 43200 is that right

 

[rock.freak667]

$$\frac{1}{2}*\frac{18}{1000}*1200^2=F*2.5$$
And so
$$12960=2.5F =>F=5184N$$