Question

A bullet is moving at a speed of 10 m/s.It strikes a wooden Planck and penetrates 4 cm before coming to stop. The time taken by the bullet to stop?

Answer 1

Given ,

u = 10 m/s

v = 0

s = 4cm = 0.04 m

so using 3rd equation of motion .

=) v ^2 = u ^2 + 2as

=) a = (v^2 - u^2 )/2s

=( 0 - 100)/0.08

= - (100×100)/8 = - 1250 m/s^2

so using above data ,

v = 0

u = 10

a = - 1250

=) using 1st equation of motion .

v = u + at

=) 0 = 10 - 1250t

=) t = 10/1250 = 1/125 sec ans.