Laws of Motion Test

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Laws of Motion Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

kg ms$$^{-1}$$ is the SI unit of

A
impulse

B
force

C
angular velocity

D
none of these

Solution

Impulse $$(I)$$ imparted to the body is equal to the change in linear momentum $$(\Delta p)$$ of the body.
Impulse $$I = \Delta p$$
Thus momentum has the same units as that of impulse.
Since momentum has SI unit as $$kg \ m/s$$, thus impulse also has SI unit as $$kg \ m/s$$.
Question 2
1 / -0

A body of mass $$5 kg$$ undergoes a change in speed form $$30 m/s$$ to $$40 {m}/{s}$$. Its momentum would increase by

A
$$50 kg {m}/{s}$$

B
$$75 kg {m}/{s}$$

C
$$150 kg {m}/{s}$$

D
$$350 kg {m}/{s}$$

Solution

change in momentum = 5 (40 - 30) = $$50kgm/s$$
Question 3
1 / -0

Newton used the phrase 'quantity of motion' for

A
Momentum

B
Force

C
Acceleration due to gravity

D
None of these

Solution

quantity of motion in a body, the relative amount of its motion, as measured by its momentum, varying as the product of mass and velocity.which is define as momentum.
Question 4
1 / -0

Momentum has the same units as that of

A
Impulse

B
Torque

C
Moment of momentum

D
Couple

Solution

Impulse applied to an object produces an equivalent vector change in its linear momentum, also in the same direction. The SI unit of impulse is the newton second $$(N⋅s)$$, and the dimensionally equivalent unit of momentum is the kilogram meter per second $$(kg⋅m/s).$$
Question 5
1 / -0

A number of discs, each of momentum $$M kg {m}/{s}$$ are striking a wall at the rate of $$n$$ discs per minute. The force associated with these discs, in newtons, would be

A
$$\displaystyle\frac{Mn}{60}$$

B
$$60 Mn$$

C
$$\displaystyle\frac{M}{60n}$$

D
$$\displaystyle\frac{n}{60M}$$

Solution

The force is $$F=\dfrac{\Delta P}{dt}$$
$$momentum=M kg.m/s$$
change in time=rate of dics striking wall
$$\Delta t=\dfrac{1}{n/minute}=\dfrac{60}{n}$$
$$F=\dfrac{\Delta P}{dt}=\dfrac{M}{60/n}=\dfrac{Mn}{60}N$$
Question 6
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

$$momentum=mass*\delta v=5kg*(20-0.20)=99kgm/s$$
Hence it decreases by $$99kgm/s$$
Question 7
1 / -0

A body of mass $$0.1 kg$$ is moving with a velocity of $$15 {m}/{s}$$. The momentum associated with the ball will be

A
$$0.5 kg {m}/{s}$$

B
$$1.5 kg {m}/{s}$$

C
$$2.5 kg {m}/{s}$$

D
$$3.2 N s$$

Solution

P =mv = 0.1 x 15 $$kgm/s$$ = 1.5$$kgm/s$$
Question 8
1 / -0

The combined effect of mass and velocity is taken into account by a physical quantity called

A
Torque

B
Moment of force

C
Momentum

D
Moment of momentum

Solution

P = mv
i.e it takes in account the factors of both m and v .
Question 9
1 / -0

A long-jumper runs before jumping because

A
He covers a greater distance

B
He maintains momentum conservation

C
He gains energy by running

D
He gains momentum

Solution

to gain momentum so that the range that he jumps is long
Question 10
1 / -0

The force acting on an object are balanced, then the object:

A
must be at rest

B
must be moving

C
must not be accelerating

D
must lose energy

Solution

Balanced forces always result in a zero external force acting on an object i.e $$F_{ext} =0$$
$$\therefore$$ Acceleration $$a = \dfrac{F_{ext}}{m} = 0$$
Thus the object must not be accelerating or it must be moving with constant velocity or remain at rest (if it was at rest initially). Hence option C is correct.

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Re-Attempt Weekly Quiz Competition

Laws of Motion Test - 23

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Laws of Motion Test - 23

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Question 1

impulse

force

angular velocity

none of these

Solution

Question 2

$$50 kg {m}/{s}$$

$$75 kg {m}/{s}$$

$$150 kg {m}/{s}$$

$$350 kg {m}/{s}$$

Solution

Question 3

Momentum

Force

Acceleration due to gravity

None of these

Solution

Question 4

Impulse

Torque

Moment of momentum

Couple

Solution

Question 5

$$\displaystyle\frac{Mn}{60}$$

$$60 Mn$$

$$\displaystyle\frac{M}{60n}$$

$$\displaystyle\frac{n}{60M}$$

Solution

Question 6

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 7

$$0.5 kg {m}/{s}$$

$$1.5 kg {m}/{s}$$

$$2.5 kg {m}/{s}$$

$$3.2 N s$$

Solution

Question 8

Torque

Moment of force

Momentum

Moment of momentum

Solution

Question 9

He covers a greater distance

He maintains momentum conservation

He gains energy by running

He gains momentum

Solution

Question 10

must be at rest

must be moving

must not be accelerating

must lose energy

Solution

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