Question

A bullet with a velocity of 300m/s is just able to pierce a block of wood 2.0 cm thick. If it is required to pierce a block of wood 18cm thick, it's velocity should be ​

Answer 1

Answer:

A bullet moving with a velocity of 300 m/sec is just able to pierce a block of wood 2.0cm thick. if it is required to pierce a block of wood 18cm thick ots velocity should be a. 90m/sec.

Answer 2

Answer:

Given that:-

→m = 81gm = 0.081Kg

→u = 300m/sec

→s = 10cm = 0.1m, v = 0

As the force of resistance is acting in the opposite direction of motion of bullet, hence force of resistance will produce retardation on the bullet,

Apply, V² = u² – 2as

0 = 300² – 2a(0.1)

a = 450000m/sec²

Let F is the force of resistance offered by wood to the bullet.

Using equation,

F = ma F = 0.081 X 450000

F = 36450N

Let v = velocity of bullet with which the bullet emerges from the piece of wood of 5cm thick,

U = 300m/sec, a = 450000m/sec², s = 0.05m

Using equation,

V² = u² – 2as V² = 3002 – 2 X 450000 X 0.05

V = 212.132m/sec