A metre scale is moving with uniform velocity. This implies

question, a metre scale is moving with uniform velocity that means velocity of meter scale is constant also we know change in constant quantity is zero so rate of change of velocity (i.e. acceleration) will also be zero.

Now from Newton’s 2^nd law i.e. _net but we have a(acceleration) is zero i.e. , so . _net

∴ Net force on metre scale must be zero so from our options (c) & (d) are absolutely wrong.

Now torque is the cross product of position vector and force vector also we have force vector in this case is zero i.e. _net

And torque is so putting force vector value

hence from here it is obvious that options (a) is wrong.

Therefore, option (b) is correct.