In the barrel of a rifle, a 15 gram bullet is accelerated uniformly from rest to

Question

In the barrel of a rifle, a 15 gram bullet is accelerated uniformly from  rest to a speed of 320 m/s before exiting the barrel, which is 0.78 m long. What is the approximate magnitude of the acceleration experienced by the bullet?  

a) 1.3 x 10^5 m/s^2 

b) 8.2 x 10^4 m/s^2 

c) 7.0 x 10^4 m/s^2

# d) 6.6 x 10^4 m/s^2 

e) none of the above are even approximately correct

If the barrel of the rifle in the  previous problem were held horizontally at a height of 1.5 m above level ground, approximately how far from the end of the barrel would the bullet (that exited at 320 m/s) strike the ground? Ignore the fact that air resistance will slow the bullet.  

a) 78 m  

b) 140 m 

# c) 180 m  

d) 220 m  

e) none of the above are even approximately correct

Explanation / Answer

a) a=v2/(2s) = 320*320/(2*0.78)=102400/1.56=65641 m/s2
b) t = (2 * h/g)½=(2*1.5/9.81)½ = 0.55 s
s = v * t = 320 * 0.55 = 176m

So your # answers are correct!

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