Question

A block A of mass 2 kg rests on a horizontal surface. Another block B of mass 1 kg moving at a speed of 1 m/s when at a distance of 16 cm from A collides elastically with A. The coefficient of friction between the horizontal surface and each of the blocks is 0.2 Then (g = 10 m/s² ) 

(a)  after collision block B rebounds 

(b)   after collision block B comes to rest 

(c)  final separation between blocks is 3 cm 

(d)  final separation between blocks is 5 cm 

Answer 1

Correct option  (a) after collision block B rebounds (d) final separation between blocks is 5 cm

Explanation:

Limiting friction between A and the surface : 

f =  μmg = 0.2 x 2 x 10 = 4 N

Speed of block B at the time of collision :

v ² – u² = 2as 

⇒ v² – u² =  -2 μg s 

⇒ v² = 1 – 2 x 0.2 x 10 x 0.16 = 0.36  

⇒ v = 0.6 m/s 

(a) Speed of block B after collision : 

(d)  Speed of block A after collision : 

Distance moved by block A before coming to rest : s_A = vA²/2μg = 4 cm

Distance moved by block B before coming to rest : S_B = vB²/2μg = 1 cm