Question

A bullet moving with a velocity of 165 m/s penetrates through a plank. The bullet has a velocity of 143 m/s the moment it comes out of the plank. The number of planks through which it can penetrate before it comes to rest are

Answer 1

Answer:

equation of motion can be be applied:v

2

=u

2

+2as, where acceleration is -ve.

Hence v

2

=u

2

–2as.

v(final velocity) = 0.

Therefore, u

2

=2as.

i.e. s is proportional to u

2

=

s

2

s

1

=

u

2

2

u

1

2

Therefore, s

2

=

u

1

2

u

2

2

×s

1

=

100

2

200

2

×2(planks)=8planks