Question

A bullet of mass 50g is moving with a velocity of 500m/s. It penetrates 10cm into a still target and comes to rest. Calculate the kinetic energy possessed by the bullet and the opposing force offerd by the target.

Answer 1

Retarding force

m = 50 g = 50 × 10-3 kg, u = 500 ms-1, s = 10 cm, v = 0

(i) KE = 1/2mv2 = 1/2×50 × 10-3 × (500)2 = 6250 J. 

(ii) Using v2  u2 = 2aS, we get 

a = {v2  u2}/{2aS} = {02 (500)2}/{2 × 10 ×10-2} 

= 1250000ms-2.

Therefore, retarding force, F = ma = 50 × 10-3 × 1250000 = 62500 N. .

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