Laws of Motion Test

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Laws of Motion Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

A body P has mass 2 m and velocity 5 v. Another body Q has mass 8 m and velocity 1.25 v. Find out the ratio of momentum of P and Q.

A
2:1

B
1:1

C
1:2

D
3:2

Solution

The momentum is given as $$M= mv$$
Where, $$m= $$ mass of object,
$$v= $$ velocity of object
Momentum of first object $$= 2m\times 5v = 10mv$$
Momentum of second object $$= 8m\times 1.25v=10mv$$, taking the ratio of the magnitude of momentum of Ist and IInd objects $$ |p_1|:|p_2|= 1:1$$
Hence, correct answer is B.
Question 2
1 / -0

Momentum of a body is defined to be the product of its mass and:

A
speed

B
velocity

C
acceleration

D
none of these

Solution

The momentum is given by mass times it's velocity, and it is a vector quantity with direction same as velocity. The question states momentum is mass times it's speed, which is incorrect since it gives a scalar value. Hence the statement is false and correct answer is B.
Question 3
1 / -0

The linear momentum of a ball of mass $$50 g$$ is $$0.5 kg { m s }^{ -1 }$$. Find its velocity.

A
$$0.01$$ $${ m s }^{ -1 }$$

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

C
$$5$$ $${ m s }^{ -1 }$$

D
$$10$$ $${ m s }^{ -1 }$$

Solution

We know that $$ p= mv$$
where $$p =0.5 kg ms^{-1}$$ linear momentum
$$m=50g = 0.05kg$$ mass, $$v =$$ velocity
$$\therefore v = \dfrac{p}{m}$$
$$\Rightarrow =\dfrac{0.5}{0.05} = 10 m/s$$
Question 4
1 / -0

'The action and reaction are equal in magnitude'. Is this statement true and which law is related with it ?

A
Yes, Newton's second law.

B
Yes, Newton's third law.

C
No, Newton's third law.

D
Yes, Newton's first law.

Solution

The magnitude of reaction force is exactly equal to the action force but the directions are opposite.
Question 5
1 / -0

If a car and a truck are moving with same momentum, the velocity of car is ........... the velocity of truck.

A
Greater than

B
Lesser than

C
Equal to

D
might be lesser than

Solution

We know, p$$=$$mv and the mass of car is less than truck.
However momentum are same, that shows velocity of car is greater than the velocity of truck.
Question 6
1 / -0

What is the momentum versus velocity graph is like, when mass is fixed ?

A
Straight line

B
Exponential curve

C
Parabola

D
Circle

Solution

Momentum (Linear momentum) for moving body is defined as the product of mass and velocity. If a body is moving with velocity, v and having mass, m then momentum of body is p $$= m\times v$$. SI unit of momentum (p) is kgm$${s}^{-1}$$.
F$$=\frac{dp}{dt}$$
F$$=m({v}_{2}-{v}_{1}$$)
Hence nature of graph will be straight line.
Question 7
1 / -0

A batsman hits back a ball straight in the direction of the bowler without changing its initial speed of $$12 ms^{-1}$$. If the mass of the ball is $$0.15\ kg$$, determine the change in momentum of the ball. (Assume linear motion of the ball)

A
$$3.6 kg m/s$$

B
$$5 kg m/s$$

C
$$3.5 kg m/s$$

D
$$7 kg m/s$$

Solution

The initial momentum of ball $$P_1 = m\vec{v} $$, after batsman hits ball and reverses its direction, momentum of ball $$P_2= -m\vec{v} $$
Magnitude of change in momentum $$\Delta p = \left | P_2-P_1\right | =\left | - 2m \vec{v}\right | =2m \left | \vec{v}\right | $$
from data given in question $$ m=0.15 kg ;\; \left | \vec{ v} \right |= 12m/ s$$
$$\Delta P=2\times 0.15\times 12= 3. 6 kg m/ s $$
Question 8
1 / -0

A loaded transport truck with a mass of 38000 kg is travelling at 1.20 m/s. What will be the velocity of a 1400 kg car if it has the same momentum?

A
32.57 m/s

B
30 m/s

C
15 m/s

D
32.67 m/s

Solution

Momentum of truck $$ P_{truck}= m_{truck}v_{truck}$$
from given data in question $$ m_{truck} = 38000 \; kg;\; v_{truck}= 1.2\; m/s$$
$$P_{truck}= 38000\times 1.2= 45600 \; kg m/ s$$
the momentum of car is equal to momentum of truck $$P_{car}= m_{car}v_{car}\Rightarrow v_{car}= 45600/ 1400= 32.57 m/s$$
Question 9
1 / -0

If the net force on an object is zero, then the object:

A
is in equilibrium

B
is not in equilibrium

C
may or may not be in equilibrium

D
always has zero mass

Solution

If the net force on an object is zero, then the object is in equilibrium. It means the sum of the forces in all directions must be equal to zero.
Question 10
1 / -0

A ball rolling along a floor doesn't continue rolling indefinitely. This is because of:

A
Friction

B
Mass of the body

C
earth's gravity

D
force of attraction

Solution

Force of Friction
It is the force of friction which is acting upon the ball and reducing its speed and finally making it zero.

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Re-Attempt Weekly Quiz Competition

Laws of Motion Test - 20

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Laws of Motion Test - 20

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Rank

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SHARING IS CARING

Question 1

2:1

1:1

1:2

3:2

Solution

Question 2

speed

velocity

acceleration

none of these

Solution

Question 3

$$0.01$$ $${ m s }^{ -1 }$$

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

$$5$$ $${ m s }^{ -1 }$$

$$10$$ $${ m s }^{ -1 }$$

Solution

Question 4

Yes, Newton's second law.

Yes, Newton's third law.

No, Newton's third law.

Yes, Newton's first law.

Solution

Question 5

Greater than

Lesser than

Equal to

might be lesser than

Solution

Question 6

Straight line

Exponential curve

Parabola

Circle

Solution

Question 7

$$3.6 kg m/s$$

$$5 kg m/s$$

$$3.5 kg m/s$$

$$7 kg m/s$$

Solution

Question 8

32.57 m/s

30 m/s

15 m/s

32.67 m/s

Solution

Question 9

is in equilibrium

is not in equilibrium

may or may not be in equilibrium

always has zero mass

Solution

Question 10

Friction

Mass of the body

earth's gravity

force of attraction

Solution

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