## Quiz 8 :

Rotational Motion and Equilibrium

Answer:

A rigid body is an object or a system of particles in which the distance between any two particles is fixed.

Option (a) is correct answer because in pure rotational motion all of the particles of the object have the same instantaneous angular velocity.

Option

is not correct because in pure rotational motion all the particles of a body have not the same tangential velocity because different particles are at different distances from the axis.

Option

is not correct because in pure rotational motion the acceleration is not always zero as the velocity of the particles changes continuously.

Option

is not correct because in pure rotational motion all particles in the body rotate about the same axis.

Answer:

In pure rotational motion, all the particles in the object have same instantaneous angular velocity. The condition for rolling without slipping is,

Here, r is radius of object, and

is angular velocity.

Rearrange the equation for

.

The radius of ball is 15 cm. convert units of radius from cm to m.

Substitute 0.25 m/s for

, and 0.15 m for r in equation

Therefore, the angular speed of ball is

.

Answer:

Rolling is combination of translational and rotational motions. Adding the velocity vectors of these two motions shows that the point of contact is instantaneously at rest.

Option (a) is not correct because the axis of rotation changes with time in roiling motion.

Option (b) is correct because in rolling motion, the point of contact with surface is instantaneously at rest.

Option (c) is not correct if

, the body will role without slip.

Option (a) and option (c) are not correct, so potion (d) is not correct.