Laws of Motion Test

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Laws of Motion Test - 19

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Question 1
1 / -0

The unit of linear momentum is:

A
$$N$$ $$s$$

B
$$kg$$ $$m$$ $${ s }^{ -2 }$$

C
$$N$$ $${ s }^{ -1 }$$

D
$$k{ g }^{ 2 }$$ $$m$$ $${ s }^{ -1 }$$

Solution

Linear momentum, $$p=mv$$
Unit of mass $$=kg$$
Unit of velocity $$=m/s$$
Hence, Unit of linear momentum $$=kg m/s = kg m/s^2\times s = Ns$$
Question 2
1 / -0

Momentum is closely related to:

A
force

B
impulse

C
velocity

D
kinetic energy

Solution

Momentum of an object is due to its mass and velocity. m x v = momentum. Mass remains constant for any object. The value of momentum mostly depends on the value of velocity. Thus, velocity out of the four options is closely related to momentum.
Question 3
1 / -0

Two balls A and B of masses $$m$$ and $$2m$$ are in motion with velocities $$2v$$ and $$v$$ respectively. What is the ratio of their momentum ?

A
1:2

B
2:1

C
1:1

D
4:1

Solution

(i) Inertia depends on mass, and since the mass of the two balls are $$m$$ and $$2m$$, So the ratio of inertia of the balls $$1 : 2$$

(ii)Momentum , $$ p = mv$$
So, as per momentum equation, it depends on both mass and velocity.
So, their ratio $$= m \times 2v : 2m \times v = 1: 1$$
Question 4
1 / -0

A body of mass $$5 kg$$ is moving with velocity $$2 { ms }^{ -1 }$$. Calculate its linear momentum.

A
$$2.5$$ $$kg$$ $${ ms }^{ -1 }$$

B
$$10$$ $$kg$$ $${ ms }^{ -1 }$$

C
$$5$$ $$kg$$ $${ ms }^{ -1 }$$

D
$$20$$ $$kg$$ $${ ms }^{ -1 }$$

Solution

We know that $$ p= mv$$

where $$p =$$ linear momentum

$$m=5kg$$ mass, $$v =2 m/s$$ velocity

$$ p = 5 \times 2 = 10 kg ms^{-1}$$
Question 5
1 / -0

Momentum is most closely related to :

A
force

B
impulse

C
KE

D
power

Solution

Force is defined as the rate of change of momentum.
It is given by $$\dfrac {\text{change of momentum}}{time} $$.
Impulse is defined as the change of momentum. It is given by $$ {Force} \times {time} $$.
Kinetic energy is the energy possessed by an object because of its motion. It is given by $$ \dfrac 12mv^2$$. It can't be calculated by momentum alone. Power is the rate of work done with respect to time. it is not related to momentum.
Among force and impulse, There is a lesser calculation for impulse. Also, it has same dimensions as momentum. Hence that is most closely related.
Question 6
1 / -0

A gun requiring the support of shoulder shows intensive recoil when fired with:

A
the butt held tightly with the shoulder.

B
the butt held loosely against the shoulder.

C
butt held loosely or tightly against the shoulder.

D
a bullet of greater mass.

Solution

Let $$m$$ be the mass of the bullet and $$M$$ be the mass of the gun. If $$v$$ is the velocity of bullet then applying Linear Momentum Conservation
$$MV = mv $$ i.e., $$V = \displaystyle \frac{mv}{M}$$
Thus, $$V$$ is the velocity of recoil of gun when held loosely.
But when the gun is held tightly with the shoulder, the mass of the man supports the gun thus reducing the speed of gun. Hence, the gun experiences intensive recoil when fired with the butt held loosely with the shoulder.
Question 7
1 / -0

The SI unit of momentum is :

A
$$kg ms^{-1}$$

B
$$kg m s^{-2}$$

C
$$kg m s^{2}$$

D
$$kg m^{-1}s^{-1}$$

Solution
Question 8
1 / -0

A ball tied to a string is swung in a vertical circle. Which of the following remains constant?

A
Tension in the string.

B
Speed of the ball.

C
Centripetal force.

D
Earth's pull on the ball.

Solution

Earth's pull on the ball remains constant $$(W=mg)$$.
Tension in the string changes along the vertical circular path.
Speed of the ball changes as sum of kinetic energy and potential energy remains constant during motion.
Speed changes, hence, centripetal force changes.
Question 9
1 / -0

Newton's third law:

A
defines the force qualitatively

B
defines the force quantitatively

C
explains the way the force acts on a body

D
gives the direction of force

Solution
Question 10
1 / -0

If the acceleration of an object is zero:

A
it must be at rest

B
it may or may not be at rest

C
it must be moving

D
it must be falling freely under gravity

Solution

From newton's 2nd law of motion, the zero acceleration implies no external force, however, the body may have uniform velocity.
Hence the body may or may not be at rest.

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Re-Attempt Weekly Quiz Competition

Laws of Motion Test - 19

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Laws of Motion Test - 19

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SHARING IS CARING

Question 1

$$N$$ $$s$$

$$kg$$ $$m$$ $${ s }^{ -2 }$$

$$N$$ $${ s }^{ -1 }$$

$$k{ g }^{ 2 }$$ $$m$$ $${ s }^{ -1 }$$

Solution

Question 2

force

impulse

velocity

kinetic energy

Solution

Question 3

1:2

2:1

1:1

4:1

Solution

Question 4

$$2.5$$ $$kg$$ $${ ms }^{ -1 }$$

$$10$$ $$kg$$ $${ ms }^{ -1 }$$

$$5$$ $$kg$$ $${ ms }^{ -1 }$$

$$20$$ $$kg$$ $${ ms }^{ -1 }$$

Solution

Question 5

force

impulse

KE

power

Solution

Question 6

the butt held tightly with the shoulder.

the butt held loosely against the shoulder.

butt held loosely or tightly against the shoulder.

a bullet of greater mass.

Solution

Question 7

$$kg ms^{-1}$$

$$kg m s^{-2}$$

$$kg m s^{2}$$

$$kg m^{-1}s^{-1}$$

Solution

Question 8

Tension in the string.

Speed of the ball.

Centripetal force.

Earth's pull on the ball.

Solution

Question 9

defines the force qualitatively

defines the force quantitatively

explains the way the force acts on a body

gives the direction of force

Solution

Question 10

it must be at rest

it may or may not be at rest

it must be moving

it must be falling freely under gravity

Solution

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