221. Two rotating bodies $$A$$ and $$B$$ of masses $$m$$ and $$2\,m$$  with moments of inertia $${I_A}$$ and $${I_B}\left( {{I_B} > {I_A}} \right)$$   have equal kinetic energy of rotation. If $${L_A}$$ and $${L_B}$$ be their angular momenta respectively, then

A $${L_A} = \frac{{{L_B}}}{2}$$
B $${L_A} = 2{L_B}$$
C $${L_B} > {L_A}$$
D $${L_A} > {L_B}$$
Answer :   $${L_B} > {L_A}$$
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222. There is a flat uniform triangular plate $$ABC$$  such that $$AB = 4\,cm,BC = 3 cm$$     and angle $$ABC = {90^ \circ }.$$   The moment of inertia of the plate about $$AB,BC$$  and $$CA$$ as axis is respectively $${I_1},{I_2}$$  and $${I_3}.$$ Which one of the following is true?
Rotational Motion mcq question image

A $${I_3} > {I_2}$$
B $${I_2} > {I_1}$$
C $${I_3} > {I_1}$$
D $${I_1} > {I_2}$$
Answer :   $${I_2} > {I_1}$$
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223. A particle of mass $$2\,kg$$  is on a smooth horizontal table and moves in a circular path of radius $$0.6\,m.$$  The height of the table from the ground is $$0.8\,m.$$  If the angular speed of the particle is $$12\,rad\,{s^{ - 1}},$$   the magnitude of its angular momentum about a point on the ground right under the centre of the circle is

A $$14.4\,kg\,{m^2}{s^{ - 1}}$$
B $$8.64\,kg\,{m^2}{s^{ - 1}}$$
C $$20.16\,kg\,{m^2}{s^{ - 1}}$$
D $$11.52\,kg\,{m^2}{s^{ - 1}}$$
Answer :   $$14.4\,kg\,{m^2}{s^{ - 1}}$$
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224. If $$F$$ is the force acting on a particle having position vector $$r$$ and $$\tau $$ be the torque of this force about the origin, then

A $$r \cdot \tau \ne 0\,{\text{and}}\,F \cdot \tau = 0$$
B $$r \cdot \tau > 0\,{\text{and}}\,F \cdot \tau < 0$$
C $$r \cdot \tau = 0\,{\text{and}}\,F \cdot \tau = 0$$
D $$r \cdot \tau = 0\,{\text{and}}\,F \cdot \tau \ne 0$$
Answer :   $$r \cdot \tau = 0\,{\text{and}}\,F \cdot \tau = 0$$
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