Question
Sat January 19, 2013 By: Tm Ashima

In a ballistic demonstration a police officer fires a bullet of mass 50.0g with speed 200m/s on soft plywood of thickness 2.00cm.the bullet emerges only with 10% of initial kinetic energy.the emergent speed of bullet is?

Expert Reply
Sun January 20, 2013
mass of bullet = 50 g = 0.05 Kg
speed of bullet = 200m/s
initial kinetic energy of bullet = 1/2 mv2
initial K.E = 0.5*0.05*200*200=1000 Joules
now bullet emerges only with 10% ofd initial kinetic energy 
so kinetic energy of emergent bullet is only 10% of 1000 J i.e 100J
now kinetic energy of emergent bullet is 100 J
then speed of emergent bullet is V =
on solving we get V =  =  =  =63.24 m/s
so emergent speed of bullet is 63.24 m/s
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