Three children are sitting on a see-saw in such a way that is balances. A `20 kg` and a `30 kg` boy are on opposite sides at a distance of `2m` from the pivot. It the third boy jumps off, thereby destroying balance, then the initial angular acceleration of the board is: (Neglect weight of board)

Options

A. `0.01rads^(-2)`
B. `1.0rads^(-2)`
C. `10 rads^(-2)`
D. `100rads^(-2)`

Answer

B

Explanation

Net torque `tau=30gxx2-20gxx2=20g`
`I=30xx2^(2)+20xx1^(2)-120+80=200kgm^(2)`
`tau=tau/I=(20g)/200+g/1010=1.0rads^(-2)`