Assertion: A uniform cubical block (of side a ) undergoes translational motion on a smooth horizontal surface under action of horizontal force F as shown. Under the given condition, the horizontal surface exerts normal reaction non-uniformly on lower surface of the block. Reason: For the cubical block given in statement 1 , the horizontal force F has tendency to rotate the cube about its centre in clockwise sense. Hence, the lower right edge of cube presses the horizontal surface harder in comparison to the force exerted by lower left edge of cube on horizontal surface.

If Assertion is true but Reason is false.

If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

If both Assertion and Reason are false.

If F → be a force acting on a particle having the position vector r → and τ → be the torque of this force about the origin. Then

r → · τ → = 0 and F → · τ → = 0

r → × τ → = 0 and F → × τ → ≠ 0

r → × τ → ≠ 0 and F → × τ → ≠ 0

r → × τ → ≠ 0 and F → × τ → = 0

r → × τ → ≠ 0 and r → · τ → ≠ 0

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Assertion: A rigid disc rolls without slipping on a fixed rough horizontal surface with uniform angular velocity. Then the acceleration of the lowest point on the disc is zero.

Reason: For a rigid disc rolling without slipping on a fixed rough horizontal surface, the velocity of the lowest point on the disc is always zero.

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Important Questions on Rotational Mechanics

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-2>Q 33

Assertion: A uniform cubical block (of side $a$ ) undergoes translational motion on a smooth horizontal surface under action of horizontal force $F$ as shown. Under the given condition, the horizontal surface exerts normal reaction non-uniformly on lower surface of the block.

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Reason: For the cubical block given in statement $1$ , the horizontal force $F$ has tendency to rotate the cube about its centre in clockwise sense. Hence, the lower right edge of cube presses the horizontal surface harder in comparison to the force exerted by lower left edge of cube on horizontal surface.

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 1

\vec{F}

be a force acting on a particle having the position vector

\vec{r}

and

\vec{τ}

be the torque of this force about the origin. Then

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 2

Four identical thin rods, each of mass

M

and length

l

, form a square frame. The moment of inertia of this frame about an axis through the centre of the square and perpendicular to its plane is,

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 4

The instantaneous angular position of a point on a rotating wheel is given by the equation

θ (t) = 2 t^{3} - 6 t^{2} rad

. The torque on the wheel becomes zero at time

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 5

The moment of inertia of a thin uniform rod of mass

M

and length

L

about an axis passing through its midpoint and perpendicular to its length is

I_{0} .

Its moment of inertia about an axis passing through one of its ends and perpendicular to its length is

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 6

When a mass is rotating in a plane about a fixed point, its angular momentum is directed along,

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 8

A circular platform is mounted on a frictionless vertical axle. Its radius

R = 2 m

and its moment of inertia about the axle is

200 kg m^{2}

. it is initially at rest. A

50 kg

man stands on the edge of the platform and begins to walk along the edge at the speed of

1 m s^{- 1}

relative to the ground. Time taken by the man to complete one revolution is:

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Alpha Question Bank for Medical: Physics>Chapter 10 - Rotational Mechanics>Exercise-3>Q 9

The moment of inertia of a uniform circular disc is maximum about an axis perpendicular to the disc and passing through,

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Important Questions on Rotational Mechanics

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