System of Particles and Rotational Motion Test

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System of Particles and Rotational Motion Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

Calculate the velocity of a body of a mass $$2$$ kg whose linear momentum is $$5$$ N s.

A
$$\displaystyle 2.5\ { ms }^{ -1 }$$

B
$$\displaystyle 10\ { ms }^{ -1 }$$

C
$$\displaystyle 5\ { ms }^{ -1 }$$

D
$$\displaystyle 2\ { ms }^{ -1 }$$

Solution

Linear momentum $$P = 5 \ N \ s$$
Mass $$m = 2 \ kg$$
Velocity $$V = \dfrac{P}{m} = \dfrac{5}{2} = 2.5 \ m/s$$
Question 2
1 / -0

A body of mass 5 kg undergoes a change in speed from 20 to 0.20 m/s. The momentum of the body would :

A
increase by 99 kg m/s

B
decrease by 99 kg m/s

C
increase by 101 kg m/s

D
decrease by 101 kg m/s

Solution

initial momentum of body = $$ 100 $$ kg m/s
final momentum of the body is = $$1$$ kg m/s
so change in momentum is = $$ 100-1= 99 $$ kg m/s
so the answer is B.
Question 3
1 / -0

Where should be the centre of gravity of a body ?

A
It must lie within the body

B
It may be near but not essentially within the body

C
It changes its position from time to time

D
It must be outside the body

Solution

The centre of gravity of the body lies at the point where the resultant weight of the body is supposed to act. Centre of gravity may or may not lie inside the body.
For example, centre of gravity of rim lies at its geometric centre.
Thus option B is correct.
Question 4
1 / -0

Blades of a moving fan exhibit :

A
Rotatory motion

B
Linear motion

C
Projectile motion

D
Curvilinear motion

Solution

Blades of fan revolves about the center of fan and so, the blades exhibit rotatory motion.
Question 5
1 / -0

A potter's wheel executes which type of motion?

A
Rotatory Motion

B
Curvilinear motion

C
Linear motion

D
Projectile motion

Solution

A potter's wheel revolves about its center and thus it executes rotatory motion.
Question 6
1 / -0

Centre of gravity of geometrical shaped objects will lie:

A
At its periphery

B
At its centre

C
Outside it

D
None
Solution
$$Answer:-$$ B
Center of gravity by geometrical consideration
The center of gravity of a circle is its center.
The center of gravity of a square, rectangle or a parallelogram is at the points where its diagonals meet each other.
The center of gravity of a triangle is at the point where the medians of the triangle meet.
Question 7
1 / -0

The ratio of the radii of gyration of a circular disc to that of a circular ring, each of same mass and radius, around their respective axis is :

A
$$\sqrt{3} :\sqrt {2}$$

B
$$1 :\sqrt {2}$$

C
$$\sqrt{3} : 1$$

D
$$\sqrt{5} :\sqrt {3}$$

Solution

Radius of navigation is given by
$$K=\sqrt {\frac {l}{m}}$$
For given problem
$$\frac{K_{disc}}{K_{ring}}=\sqrt{\frac{l_{disc}}{i_{ring}}}$$
$$\frac{K_{disc}}{K_{ring}}=\sqrt{\frac{\frac{1}{2}MR^2}{MR^2}}=1:\sqrt{2}$$
Question 8
1 / -0

Centre of gravity of a rectangle will be at its:

A
Centre

B
At its periphery

C
Intersection of its diagonal

D
None
Solution
$$Answer:-$$ C
Center of gravity by geometrical consideration
The center of gravity of a circle is its center.
The center of gravity of a square, rectangle or a parallelogram is at the points where its diagonals meet each other.
The center of gravity of a triangle is at the point where the medians of the triangle meet.
Question 9
1 / -0

Which is the only vector quantity out of the following?

A
Charge of a gold leaf electroscope

B
Electrostatic potential

C
Current flowing in a metal

D
Angular momentum of a spinning body

Solution

(i.) Charge of a body is a scalar quantity.$$\\$$
(ii.)Similarly, Electrostatic potential is also a scalar quantity, since it doesn't possess a direction.$$\\$$
(iii.)Even though current possesses certain direction, but when it comes to addition, it follows scalar addition.$$\\$$
(iv.)Whereas Angular momentum of a body ($$\vec L$$) has magnitude as well as direction both. Hence it is a vector quantity.
Question 10
1 / -0

A bicycle tyre in motion has :

A
linear motion only

B
rotatory motion only

C
linear and rotatory motion

D
vibratory motion only

Solution

A bicycle tyre rotates around the center which causes forward motion of the bicycle. Therefore, both rotation and linear motion of tyre is involved.

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System of Particles and Rotational Motion Test - 20

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System of Particles and Rotational Motion Test - 20

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Question 1

$$\displaystyle 2.5\ { ms }^{ -1 }$$

$$\displaystyle 10\ { ms }^{ -1 }$$

$$\displaystyle 5\ { ms }^{ -1 }$$

$$\displaystyle 2\ { ms }^{ -1 }$$

Solution

Question 2

increase by 99 kg m/s

decrease by 99 kg m/s

increase by 101 kg m/s

decrease by 101 kg m/s

Solution

Question 3

It must lie within the body

It may be near but not essentially within the body

It changes its position from time to time

It must be outside the body

Solution

Question 4

Rotatory motion

Linear motion

Projectile motion

Curvilinear motion

Solution

Question 5

Rotatory Motion

Curvilinear motion

Linear motion

Projectile motion

Solution

Question 6

At its periphery

At its centre

Outside it

None

Solution

Question 7

$$\sqrt{3} :\sqrt {2}$$

$$1 :\sqrt {2}$$

$$\sqrt{3} : 1$$

$$\sqrt{5} :\sqrt {3}$$

Solution

Question 8

Centre

At its periphery

Intersection of its diagonal

None

Solution

Question 9

Charge of a gold leaf electroscope

Electrostatic potential

Current flowing in a metal

Angular momentum of a spinning body

Solution

Question 10

linear motion only

rotatory motion only

linear and rotatory motion

vibratory motion only

Solution

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