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Please solve 3 and 4 option of this question thanks

Please solve 3 and 4 option of this question thanks

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Grade:11

1 Answers

Khimraj
3007 Points
6 years ago
Let the initial velocity of 1kg mass is u and final velocity of 5kg mass is v
then from conservation of linear momentum
1*u +5*0 = 1*(-2) + 5*v
So 5v -u = 2           – (1)
And from conservation of kinetic energy
½*1*(u)2 + 0 = ½*1*(-2)2 + ½*5*v2
So 5v2 – u2= – 4        – (2)
From solving equation (1) and (2)
v = 1, u = 3
So velocity of centre of mass 
= [1*(-2) + 5*1]/(1+5) = 3/6 = ½ 
So KE of center of mass = ½*6*( ½)2 = ¾ = 0.75J.
Total KE = ½*1*(-2)2 + ½*5*(1)2 = 2 + 5/2 = 4.5J
So (3) option is correct while option (4) is incorrect.
Hope it clears. If you like answer then please approve it.  

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