# A bullet, having a mass of 18g and traveling with a velocity of 1200 m/s strikies a

## 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

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rock.freak667
Homework Helper
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

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

rock.freak667
Homework Helper
$$\frac{1}{2}*\frac{18}{1000}*1200^2=F*2.5$$
And so
$$12960=2.5F =>F=5184N$$