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Bullet fired and penetrates a block of wood 
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#1
May1409, 07:55 PM

P: 303

1. The problem statement, all variables and given/known data[/b]
A rifle with a barrel length of 61.54 cm fires a 8.17 g bullet with a horizontal speed of 400 m/s. The bullet strikes a block of wood and penetrates to a depth of 8.9 cm. What resistive force (assumed to be constant) does the wood exert on the bullet? 2. Relevant equations Dynamics 3. The attempt at a solution 


#2
May1409, 07:55 PM

P: 303

am i even in the right direction? If not where did I go wrong?



#4
May1409, 08:10 PM

P: 303

Bullet fired and penetrates a block of wood
haha oops good catch give me a second



#5
May1409, 08:16 PM

P: 303

now its the correct image. Thank you for that.



#7
May1409, 08:19 PM

P: 303

Is that the only way that we are able to solve this because we haven't gone over engeries in class yet?



#8
May1409, 08:23 PM

Mentor
P: 41,459




#9
May1409, 08:28 PM

P: 303

Am i suppose to assume that the distance the bullet traveled is 70.44 cm? Which is the barrel length+ the depth of the bullet in the wood?



#10
May1409, 08:50 PM

P: 303

I got the anwser it was 7343.822 N.....only problem is I dont know how I got it I found someone who did this problem online and just plugged my numbers in his equation but it doesn't show how he derived the equation!



#11
May1409, 09:01 PM

HW Helper
P: 5,341

The distance it decelerates is .089 m.
The initial velocity is 400 m/s. The final velocity of course is 0. Does anything occur to you as to how to find the magnitude of the deceleration? See maybe: http://www.physicsforums.com/showpos...63&postcount=2 


#12
May1409, 09:30 PM

P: 303

I think working on physics so long actually made me worse at it. It was right in front of me I just needed you to remind me of Kinematics! just us xf=xi+(vf^2vi^2)/2a....then multiply the mass of the bullet by acceleration and that gives me fs.....wow FML



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