NEET
Practice Test 11
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Angular momentum is

  • Solution

    Angular momentum=\(\dot{r}\)×(inearmomentum)

A gymnast takes turns with her arms & legs stretched. When she pulls her arms & legs in

  • Solution

    Since no external torque act on gymnast, so angular momentum (L=Iω) is conserved. After pulling her arms & legs, the angular velocity increases but moment of inertia of gymnast, decreases in, such a way that angular momentum remains constant.

If a running boy jumps on a rotating table, which of the following is conserved?

  • Solution

    The boy does not exert a torque to rotating table by jumping,so angular momentum is conserved i.e.,

    \(\frac{d\dot{L}}{dt}=0\Rightarrow \dot{L}= constant\)

A simple pendulum is vibrating with angular amplitude of 90° as shown in figure.

For what value of θ is the acceleration directed

(i)vertically upwards

(ii)horizontally

(iii)vertically downwards

  • Solution

    When θ = 0°, the net force is directed vertically upwards.

A projectile is thrown horizontally with a speed of 20 ms-1. If g is 10 ms-2, then the speed of the projectile after 5 second will be nearly

  • Solution

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SYSTEM OF PARTICLES AND ROTATIONAL MOTION
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