Adisk shaped grindstone of mass 3.0 kg and radius 8 cm is spinning at 600 rpm. after the power is shut off the frictional torque brings the grindstone to rest in 10 s. what is the number of revolutions of the grindstone after the power is shut off?

Explanation:

It is given that,

Mass of the grindstone, m = 3 kg

Radius of the grindstone, r = 8 cm = 0.08 m

Initial speed of the grindstone,

Finally it shuts off,

Time taken, t = 10 s

Let is the angular acceleration of the grindstone. Using the formula of rotational kinematics as :

Let is the number of revolutions of the grindstone after the power is shut off. Now using the third equation of rotational kinematics as :

or

So, the number of revolutions of the grindstone after the power is shut off is 50.

probably not if net force is zero

the tires are rotating at 0.434 rpmlinear speed=45 m/sdiameter=0.550 mradius=0.275 mnow v= rωω= v/rω=45/0.275ω=163.6 rad/sω=163.6 rad/s (1rev/2π rad) (60s/1m)ω=1563 rpm