A metal coinn of mass 5 g and radius 1 cm is fixed to a thin stick AB of negligible mass as shown in the figure. The system is initially at rest. The constant torque, hat will make the system rotate about AB at 25 rotations per second in 5s. Is close to

Options

A. `1.6v xx 10^(-5) Nm`
B. `7.5 xx 10^(-6) Nm`
C. `2.0 xx 10^(-5) Nm`
D. `4.0 xx 10^(-6)` Nm

Answer

C

Explanation

`alpha = (omega_(f) - omega_(i))/(Delta) = (25 xx 2pi)/5 = 10 pi (rad)/s^(2), tau = Ialpha =((MR^(2))/4 + MR^(2)) alpha = 5/4 MR^(2) = 1.96 xx 10^(-4) therefore 2.0 xx 10^(-6)` Nm