Question

A bullet of mass 15g has a speed of 400m/s.What is its kinetic energy? If bullet strikes a thick target and is brought to rest in 2cm,calculate the average net force acting on the bullet.what happens to the kinetic energy originally in the bullet?

Answer 1

mass=15g=0.015kg
velocity=400m/s
Kinetic energy=1/2 x mv^2=0.015/2×(400)^2 =1200 kg-m /s
final velocity v=0
initial velocity u=400m/s
distance=2cm=0.02 m
using eqn of motion
a = (v^ - u^2 )/2s
   = - 160000/(2×0.02)
a= - 4000000m/s^2 negative sign is for retardation.

force=ma force=0.015×4000000 =60000N 

i hope it will help you
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