    Question

# Two spheres of masses 2M and M are initially at rest at a distance R apart. Due to the mutual force of attraction, they approach each other. When they are at a separation R2 ,the acceleration of the centre of mass of spheres would be

A
0 ms2
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B
1ms2
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C
3ms2
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D
12ms2
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Solution

## The correct option is A 0 ms−2Given,Mass of sphere 1=M1=2MMass of sphere 2=M2=MDistance between both sphere initially =RTo find, acceleration of centre of mass (CM) at distance R/2,Here,⇒ Intial velocity of both sphere is Dms−1Here, Momentum is∴M1u1+M1u2=(M1+M2)V∴M1(0)+M2(0)=(M1+M2)V .... (V⇒ velocity of CM i.e. whole system)∴V=0⇒ There is mutual force of attraction.∴ Force f1=GM1M2r2 f2=GM1M2r2As both forces are same, & no external force, ∴fnet=0Now for acceleration of CM⇒f=Ma∴Ma=0∴a=0m/s2Hence, acceleration is 0m/s2Hence, option (A) is correct.   Suggest Corrections  0      Similar questions
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