
#1
Oct2208, 04:06 PM

P: 1

1. The problem statement, all variables and given/known data
A 7.0g bullet is fired into a 1.5kg ballistic pendulum. The bullet emerges from the block with a speed of 200 m/s, and the block rises to a maximum height of 12 cm. Find the initial speed of the bullet. Now I think this is an imperfect inelastic collision because the bullet does not lodge itself in the pendulum. So I assumed since it was inelastic I could ignore conservation of kinetic Energy. 2. Relevant equations Conservation of Momentum Conservation of Energy 3. The attempt at a solution m1v1i +m2v2i=(m1 + m2)vf (.007kg x v1i)+0=(1.507kg)vf (PE + KE)collision=(PE + KE)top 0 + (.5 x 1.507 x vf^2)= mgh + .5mv^2 0 + (.5 x 1.507kg x vf^2) = (1.5 kg x 9.81m/s^2 x .12m) + (.5 x .007kg x 200^2) vf^2=(1.7658J + 140J)/(.7535kg) vf=13.716m/s (.007kg x v1i)=1.507kg x 13.716m/s v1i = 2952 m/s Now I know this is not the answer because the answer is given as 530m/s but I can't for the life of me figure out what went wrong with the energy calculation. (I'm assuming that's where the big boo boo happened) 



#2
Oct2208, 11:02 PM

HW Helper
P: 2,250

Hi rbrow039,



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