Two particles are shown in figure. At `t = 0` a constant force `F = 6 N` starts acting on `3 kg`. Find the velocity of circle of mass of these particle at `t = 5 s`.
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Options

A. `5m//s`
B. `4m//s`
C. `6m//s`
D. `3m//s`

Answer

C

Explanation

Method1: Accelerationof `3 kg`
`a_(2)=6/3=2m//s^(2)`
Velocity of `3 kg` at `t=5 s:v_(2)=u_(2)+a_(2)t=0+2x5=10m//s`
`v_(CM(t=5s))=(2xx0+3x10)-(2+3)=6m//s`
Method 2:
`a_(CM)=F/(m_(1)+m_(2))=6/(2+3)=1.2m//s^(2)`
`v_(CM)=u_(CM)+a(CM)t=0+1.2xx5=6m//s`