Question

A bullet of mass 10 g travelling horizontally with a velocity of 150 m s-l strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block. Also calculate the magnitude ofthe force exerted by the wooden block on the bullet.

Answer 1

Data:

mass of the bullet (m) = 10 g = (10/1000) kg =0.01 kg

Initial velocity (u) = 150 m/s

Final velocity (v) = 0 m/s

Time taken (t) = 0.03 sec

i. Calculation of the distance of penetrationof the bullet into the block:  

Calculation of the distance of penetrationof the bullet into the block = Displacement

Displacement = average velocity × time

Displacement = [(u + v) / 2] × time

Displacement = [(150 + 0) / 2] × 0.03

Displacement = 2.25 m

ii. Calculation of the magnitude of the force exerted by the wooden block on the bullet:

the magnitude of the force exerted by the wooden block on the bullet = Retarding force

Retarding force = mass × reatardation

Retarding force = mass ×[ (Intitial velocity - Final velocity) / t ]

Retarding force = 0.01 ×[ (150 - 0) / 0.03 ] N

Retarding force = [150/3] N

Retarding force = 50 N

Answer 2

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