Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 22

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A disk having a thread tightly wound on it, is being pulled upwards by the thread such that the disk starts moving upwards with an acceleration $g$ . If angular acceleration is $α$ and radius $R$ , then the value of $R α$ is

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Important Questions on Rotational Motion

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 23

A flywheel of the moment of inertia

3 \times 10^{2} kg m^{2}

is rotating with a uniform angular speed of

4.6 rad s^{- 1} .

If a torque of

6.9 \times 10^{2} N m

retards the wheel, then the time in which the wheel comes to rest is

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 25

A flywheel of the moment of inertia

0.4 k g m^{2}

and radius

0.2 m

is free to rotate about a central axis. If a string is wrapped around it and it is pulled with a force of

10 N

, then its angular velocity after

4 s

will be

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 27

A uniform thin rod of length

2 L

and mass

m

lies on a horizontal table. A horizontal impulse

J

is given to the rod at one end. There is no friction. The total

KE

of the rod just after the impulse will be,

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 28

The moment of inertia of a disc about axis $O$ $O'$ is $N m r^{2}$ . Axis is in the plane of disc and tangential. Then the value of $N$ is:

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 29

The moment of inertia of a metre scale of mass

0.6 kg

about an axis perpendicular to the scale and located at the

20 cm

position on the scale is

n

kg m^{2}

(Breadth of the scale is negligible). The value of

n

is

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 30

The moment of inertia of a hollow cubical box of mass

M

and side length

a

, about an axis passing through centres of two opposite faces, is equal to

\frac{x M a^{2}}{18}

. The value of

x

is

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 1>Q 31

Which of the following statements is true in case of the principle of perpendicular axes?

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Physics Crash Course JEE Main>Chapter 5 - Rotational Motion>Level 2>Q 16

A force

\vec{F} = 4 \hat{i} - 5 \hat{j} + 3 \hat{k}

is acting at a point

{\vec{r}}_{1} = \hat{i} + 2 \hat{j} + 3 \hat{k} .

The torque acting about a point

{\vec{r}}_{2} = 3 \hat{i} - 2 \hat{j} - 3 \hat{k}

is,