An indestructible bullet 2.00 cm long is fired straight through a board that is 10.0 cm thick. The bullet strikes the board with a speed of 420 m/s and emerges with a speed of 280 m/s. (To simplify, assume that the bullet accelerates only while the front tip is in contact with the wood.)(adsbygoogle = window.adsbygoogle || []).push({});

the question asks for a)avg. acceleration of the bullet through the board?

b) total time that the bullet is in contact with board?

i found the avg. acceleration by using the formula v^2=Vinit^2 + 2aX

with V=280 Vint=420 and X=.1m and found acceleration to be -49000 m/s^2... i checked with my teacher and this answer is correct..however my answer for b) is wrong

for b) i used the equation V= Vint + at

with V=280, Vint=420 and a=-4900 and found time to = 2.87e-4

my t is wrong can somebody plz help me...i would also like to add that my teacher said that there are a few ways to interpret this question..(for this question ive ignored the fact that the bullet is 2cm long, but i dont know how to use this bit of info to solve for time)

thank you

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# Homework Help: Motion in one - dimension question

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