Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 33

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following best describe about the statement " An object slides on a horizontal, frictionless surface".

A
Inertia

B
Unbalanced forces

C
Action and reaction force pairs

D
Universal gravitation

E
Simple harmonic motion

Solution

Law of inertia states that present state (in motion or stationary) of a body does not change until an external force is applied on it .
As the object slides on a frictionless surface it means no external force is working on it ,so body will continue to slide due to inertia of motion.
Question 2
1 / -0

A book rests on a table, exerting a downward force on the table. The reaction to this force is

A
the force of Earth on the book

B
the normal force acting on the book because of the table

C
the force of Earth on the table

D
the inertia of the book

Solution

The reaction is always in opposite direction to the action and action and reaction always act on different bodies , according to Sir Newton's third law .Hence , reaction to the action of book on table will be the force of the table on the book .
Question 3
1 / -0

A ball falls freely towards the Earth. If the action force is the Earth pulling down on the ball, then identify which of the following best describe the reaction force:

A
the ball pulling up on the Earth

B
air resistance acting on the ball.

C
the ball striking the Earth when it lands.

D
the inertia of the ball

E
there is no reaction force in this case.

Solution

The earth is pulling the ball down during its motion.
According to Newton's 3rd law of motion, every action has equal and opposite reaction.
Thus the ball is also pulling the earth in the upward direction.
Question 4
1 / -0

Which one of the following is equal to $$1$$ Newton?

A
$$1\ kg\cdot m^{2}/s$$

B
$$1\ kg\cdot m/s^{2}$$

C
$$1\ kg^{2} / s$$

D
$$1\ kg^{2}\cdot m/s$$

Solution

Force acting on a body $$F = mg$$ Newton
$$\therefore$$ $$1$$ Newton $$ = 1$$ $$kg.m/s^2$$
Question 5
1 / -0

What would happen to a car traveling west at a constant velocity of 55 MPH without any influence of external force?

A
The car would continue moving west with a velocity of 55 MPH

B
The car would slowly increase its velocity approaching but not reaching the speed of light

C
The car would slow down but never reach 0 velocity

D
The car would slow down and come to rest

E
The car would increase its velocity without changing acceleration

Solution

With no external force acting on the car, the state of motion of the car would not change. Therefore, the car would continue to move with the same velocity, i.e. $$55\ MPH$$ towards the west.
Question 6
1 / -0

A physics book rests on a table top. A gravitational force pulls down on the book. According to Newton's third law. The force that is equal to this gravitational force is:

A
the force the table exerts upward on the book.

B
the force the book exerts downward on the table.

C
the force the table exerts downward on the table.

D
the force the book exerts upward on the table.

E
the force the air pressure exerts down on the book.

Solution

Sir Newton's third law of motion states that for an action there is always an equal and opposite reaction . These two forces always act on different objects . When a book is kept on a table , weight (gravitational force) of book acts on table vertically downwards and as a reaction of weight , table also exerts an equal and opposite ( upward) force on book .
Question 7
1 / -0

Consider a porter standing on a platform with a suitcase which presses his head with a force of 200 N. If this force is taken to be the action, from where is the reaction force exerted and to where is it directed ?

A
The head, on the suitcase

B
The earth, on the suitcase

C
The earth, on the porter

D
The suitcase, on the earth

Solution

According to Newton third law reaction force of 200N will be opposite to the direction of action and is upwards and caused by the porter from his head.
Question 8
1 / -0

Vehicles are provided with shock absorbers. Which of the following laws of Newton given below explain this?

A
The first law of motion

B
The second law of motion

C
The third law of motion

D
All of the above

Solution

The vehicle receives a sudden sharp movement when it moves on uneven surfaces. So, the vehicle receives impulsive force. Using the second law of motion to minimize this impact, shock absorbers are used.
$$Impulse=F(Δt)$$ (where $$F$$= force and $$\Delta t$$= small change in time)
$$F\propto \dfrac {1}{\Delta t} $$
The shock absorbers increase the time of sudden sharp movement by reducing impulsive force.
This minimizes the damage. to the vehicle.
Question 9
1 / -0

Which of the following statements is NOT true?

A
When the mass of a body is doubled, the momentum of a body is halved, provided the velocity remains the same.

B
The pain we feel in the hand on hitting the wall is a consequence of Newton's third law of motion.

C
A table-cloth which is pulled from a table without dislodging the dishes is due to inertia of rest.

D
Momentum is a vector quantity.

Solution

The momentum of a body is a product of mass and its velocity. ie $$\vec P=m\ \vec v$$ it is a vector quantity.
hence when the mass of body is doubled by keeping its velocity constant then momentum of body will be double.
hence Statement $$a$$ is wrong and statment $$d$$ is right.
According to statement given in $$b$$ is correct because according to newton's 3rd law; every action have equal and opposite reaction therefore when you will hit the wall by a force (action force), with same force wall will hit your hand (Reaction force) hence hand feel pain.
Statment $$c$$ can be explained by the properties of inertia of rest. When you pull the table cloth quickly then external force will not transfer to the dishes so it wil stay in rest.
Question 10
1 / -0

A force of a given magnitude acts on a body. On what factors does the acceleration of the body depend?

A
Density of the body

B
Volume of the body

C
Mass of the body

D
Shape of the body

Solution

$$F=ma$$
when F is constant
$$a\propto \dfrac{1}{m}$$

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Forces and Laws of Motion Test - 33

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Forces and Laws of Motion Test - 33

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Question 1

Inertia

Unbalanced forces

Action and reaction force pairs

Universal gravitation

Simple harmonic motion

Solution

Question 2

the force of Earth on the book

the normal force acting on the book because of the table

the force of Earth on the table

the inertia of the book

Solution

Question 3

the ball pulling up on the Earth

air resistance acting on the ball.

the ball striking the Earth when it lands.

the inertia of the ball

there is no reaction force in this case.

Solution

Question 4

$$1\ kg\cdot m^{2}/s$$

$$1\ kg\cdot m/s^{2}$$

$$1\ kg^{2} / s$$

$$1\ kg^{2}\cdot m/s$$

Solution

Question 5

The car would continue moving west with a velocity of 55 MPH

The car would slowly increase its velocity approaching but not reaching the speed of light

The car would slow down but never reach 0 velocity

The car would slow down and come to rest

The car would increase its velocity without changing acceleration

Solution

Question 6

the force the table exerts upward on the book.

the force the book exerts downward on the table.

the force the table exerts downward on the table.

the force the book exerts upward on the table.

the force the air pressure exerts down on the book.

Solution

Question 7

The head, on the suitcase

The earth, on the suitcase

The earth, on the porter

The suitcase, on the earth

Solution

Question 8

The first law of motion

The second law of motion

The third law of motion

All of the above

Solution

Question 9

When the mass of a body is doubled, the momentum of a body is halved, provided the velocity remains the same.

The pain we feel in the hand on hitting the wall is a consequence of Newton's third law of motion.

A table-cloth which is pulled from a table without dislodging the dishes is due to inertia of rest.

Momentum is a vector quantity.

Solution

Question 10

Density of the body

Volume of the body

Mass of the body

Shape of the body

Solution

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