# A circular disc of radius r has a uniform thickness.  A circular hole of diameter equal to the radius of the disc has been cut out as shown.  The centre of gravity of the remaining disc lies on the diameter of the disc at a distance x to the left of the centre of the original disc.  The value of x is 1. r                              2. $\frac{r}{2}$ 3. $\frac{r}{4}$                           4. $\frac{r}{6}$

Subtopic:  Center of Mass |
63%
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A 'T' shaped object with dimensions shown in the figure, is lying on a smooth floor. A force '$\stackrel{\to }{\mathrm{F}}$' is applied at the point P parallel to AB, such that the object has only the translational motion without rotation. Find the location of P with respect to C

1.  $\frac{4}{3}l$

2.  I

3.  $\frac{2}{3}l$

4.  $\frac{3}{2}l$

Subtopic:  Center of Mass |
From NCERT
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A wheel is rotating about an axis through its centre at $$720$$ r.p.m. It is acted upon by a constant torque opposing its motion for $$8$$ seconds to bring it to rest finally. The value of torque in N-m is: (given $$I$$$\frac{24}{\mathrm{\pi }}$ kg ${\mathrm{m}}^{2}$)
1. $$48$$
2. $$72$$
3. $$96$$
4. $$120$$

Subtopic:  Rotational Motion: Dynamics |
84%
From NCERT
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Assertion : The speed of whirlwind in a tornado is alarmingly high.

Reason    : If no external torque acts on a body, its angular velocity remains conserved.

1. If both assertion and reason are true and reason is the correct explanation of assertion.

2. If both assertion and reason are true but reason is not the correct explanation of assertion.

3. If assertion is true but reason is false.

4. If both assertion and reason are false.

Subtopic:  Angular Momentum |
From NCERT
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A circular disc A of radius r is made from an iron plate of thickness t and another circular disc B of radius 2r and thickness $\frac{\mathrm{t}}{4}$. The relation between moments of inertia ${\mathrm{I}}_{\mathrm{A}}$ and ${\mathrm{I}}_{\mathrm{B}}$ is

1.

2.

3.

4.  Depends on the actual values of t and r

Subtopic:  Moment of Inertia |
66%
From NCERT
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A particle of mass 2 kg located at the position  m has a velocity of 2 m/s. Its angular momentum about z-axis in kg-${\mathrm{m}}^{2}/\mathrm{s}$ is :

1. +4

2. +8

3. -4

4. -8

Subtopic:  Angular Momentum |
From NCERT
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A cylinder of mass 'M' is suspended by two strings wrapped around it as shown. The acceleration 'a' and the tension T when the cylinder falls and the string unwinds itself are, respectively,

1.

2.

3.

4.

Subtopic:  Rolling Motion (OLD NCERT) |
From NCERT
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An automobile engine develops 100 kW when rotating at a speed of 1800 rev/min. What torque does it deliver ?

1. 350 N-m

2. 440 N-m

3. 531 N-m

4. 628 N-m

Subtopic:  Torque |
69%
From NCERT
PMT - 2000
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In an orbital motion, the angular momentum vector is

1. Along the radius vector

2. Parallel to the linear momentum

3. In the orbital plane

4. Perpendicular to the orbital plane

Subtopic:  Angular Momentum |
75%
From NCERT
AIIMS - 2004
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A particle of mass m moves with a constant velocity along 3 different paths, DE, OA and BC. Which of the following statements is not correct about its angular momentum about point O?

 1 It is zero when it is at A and moving along OA. 2 The same at all points along the line DE. 3 Of the same magnitude but oppositely directed at B and  D. 4 Increases as it moves along the line BC.

Subtopic:  Angular Momentum |
53%
From NCERT
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