Using second law of motion, derive the relation between force and acceleration. A bullet of 10 g strikes a sand-bag at a speed of 103 ms-1 and gets embedded after travelling 5 cm. Calculate:

(i) The resistive force exerted by the sand on the bullet


(ii) The time taken by the bullet to come to rest.

(i) Given,

m = 10g = kg


u = 103 m/s


v = 0, s = 5cm = m


v2 – u2 = 2as


0 – (103)2 = 2 × a ×


-(103) × (10)3 =


a = (-1000 × ) × 100


= -107 ms-2


F = ma


= 1/100x - 107


= -105 N


(ii) v = u +at


0 = (103) – 107 × t


t =


t = 10-4s


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