Sun February 05, 2012 By:

A bullet of mass 30 g loses 80% of its velocity when it comes out from a sand bag within 0.3 seconds. If its initial velocity of penetration is 25 m/s, the nagnitude of resistive force acting on it is 2N. why and HOW???

Expert Reply
Mon February 06, 2012
The initial velocity= 25 m/s
the final velocity= 20% of 25 m/s= 5 m/s
so change in velocity= 20 m/s
time taken = 0.3 s
5=25+ a *0.3
a= - 200/3 m/s2
So F= m*a
F=0.030*200/3=2 N
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