91Ó°ÊÓ

The forces acting on yo-yo are $\stackrel{→}{F_1},\stackrel{→}{F_2},\stackrel{→}{F_3}$,

The torque on the rotating object is a moment of force. It is equal to the cross product of the radius vector of rotation with the force acting on the rotating object.

Use the concept of torque to find the effects of the given forces.

Formulae are as follow:

$\stackrel{→}{\mathrm{τ}}=\stackrel{→}{r}×\stackrel{→}{F}$

Where, r is radius,F is force and $\mathrm{Ï„}$is torque

Now, calculate torque due to force$\stackrel{→}{F_2}$:

The pivot point is at ground so the angle between the pivot point and the force $\stackrel{→}{F_2}$is${\mathrm{θ}}_2$

The torque will be,

$\left|\mathrm{τ}\right|=\left|{\stackrel{→}{r}}_2\right|×\left|\stackrel{→}{F_2}\right|\text{sin}{\mathrm{θ}}_2$

The applied force is along the position vector so the angle is 0.

$\left|\mathrm{τ}\right|=\left|{\stackrel{→}{r}}_2\right|×\left|\stackrel{→}{F_2}\right|\text{sin}\left(0^0\right)$

$\left|\mathrm{Ï„}\right|=0\text{Nm}$

Therefore, the magnitude of the torque is equal to zero.

Now, calculate torque due to force$\stackrel{→}{F_1}$:

$\left|\mathrm{τ}\right|=\left|\stackrel{→}{r_1}\right|×\left|\stackrel{→}{F_1}\right|\text{sin}{\mathrm{θ}}_1$

The angle is${90}^0$

$\left|\mathrm{τ}\right|=\left|\stackrel{→}{r_1}\right|×\left|\stackrel{→}{F_1}\right|\text{sin}\left({90}^0\right)$

$\left|\mathrm{τ}\right|=\left|\stackrel{→}{r_1}\right|×\left|\stackrel{→}{F_1}\right|$

From the right hand rule the direction of torque will be clockwise. So, it moves towards the right.

Now, calculate torque due to force$\stackrel{→}{F_3}$ :

From the right hand rule the direction of torque will be anticlockwise. So, it moves towards the left.

Therefore, find the torques by using the concept of torque by considering the angles.

Take a pivot point where the yoyo is in contact with ground.