In the system shown in fig the mass 30 kg is pulled by a force 210 N At the instant when the 15 kg mass has acceleration `6m//s^(2)` the acceleration of 30 kg mass will be: (Assume the spring to the massless)

Options

A. `2 m//s^(2)`
B. `3 m//s^(2)`
C. `3.4 m//s^(2)`
D. `4 m//s^(2)`

Answer

D

Explanation

`T=15xxa_(1)`
`a_(1)` = acceleration of 15 kg
`T=15xx6=90N`
Now, `210-90=30xxa_(2)`