The force mg acting on the body has two components mg sin θ and mg cos θ and the body will exert a normal reaction. Let R =
Since R and mg cos θ pass through the centre of the cube, there will be no torque due to R and mg cos θ. The only torque will be produced by mg sin θ.
i = F × r (r = a/2) (a = ages of the cube)
i = mg sin θ × a/2
= 1/2 mg a sin θ.
