Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 20

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Weekly Quiz Competition

Question 1
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 2
1 / -0

The acceleration produced in a body by a force of given magnitude depends on:

A
size of the body

B
shape of the body

C
mass of the body

D
none of these

Solution

Newton's second law of motion, $$F=ma$$, where $$m$$ is mass of an object which acquires acceleration $$a$$ when force $$F$$ is applied on it.
For a force of constant magnitude, $$a\propto{\dfrac{1}{m}}$$ i.e. acceleration is inversely proportional to mass.
Question 3
1 / -0

How does the acceleration ($$a$$) produced by a given force ($$F$$) depend on mass ($$m$$) of the body?

A
$$F=\dfrac{m}{g}$$

B
$$F=mg$$

C
$$F=ma$$

D
$$F=\dfrac{m}{a}$$

Solution

According to Newton's second law of motion, $$F=ma$$, where $$m$$ is mass of an object which acquires acceleration $$a$$ when force $$F$$ is applied on it.
For a constant force, $$a\propto{\dfrac{1}{m}}$$

Or, for a given force, acceleration is inversely proportional to the mass of the object.
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

'The action and reaction both act simultaneously.' Is this statement true and what is the net force ?

A
yes, zero

B
no, zero

C
yes, positive

D
no, negative

Solution

Action and reaction, both act simultaneously on different objects and in opposite directions. As soon as action force is removed, reaction force also ends.
Question 6
1 / -0

You pull your hands back while catching a fast moving cricket ball. Which law is used to explain it ?

A
law of inertia.

B
Newton's second law of motion

C
Newton's first law of motion

D
Newton's third law of motion

Solution

(a) A fast moving ball has a tendency to keep moving due to inertia. According to Newton's second law, the force with which ball is moving is equal to its mass multiplied by its acceleration. When we catch a ball, momentum of the ball is transferred from ball to hand. If we keep our hand stationary, the force with which momentum is transferred might hurt our hand. But as soon as we pull our hands back, net momentum is decreased, thus reducing the force with which ball makes an impact with our hands.
Question 7
1 / -0

Which is the Newton's second law of motion ?

A
$$v=u+at$$

B
$$F=ma$$

C
$$F=m/a$$

D
$$S=ut+(1/2)at^2$$

Solution

The second law states that the net force on an object is equal to the rate of change of its linear momentum $$"p".$$
$$F=\dfrac{\Delta P}{\Delta t}$$ $$=\dfrac{P_f-P_i}{\Delta t}$$
$$\implies F= \dfrac{mv-mu}{\Delta t}$$

The second law can also be stated in terms of an object's acceleration. Since Newton's second law is only valid for constant-mass systems, mass can be taken outside. So,
$$F = m \times \dfrac{v-u}{\Delta t} = F =m \times a$$
Thus, the net force applied to a body is expressed as mass times acceleration produced by the force.
Question 8
1 / -0

A force of $$10 N$$ acts on a body of mass $$5 kg$$. Find the acceleration produced.

A
$$5$$ $${ ms }^{ -2 }$$

B
$$50$$ $${ ms }^{ -2 }$$

C
$$2$$ $${ ms }^{ -2 }$$

D
$$2.5$$ $${ ms }^{ -2 }$$

Solution

F = 10 N, m = 5 kg
Putting the values in $$F=m\times a$$
$$10=5\times a$$
$$a=2 m/s^2$$
Question 9
1 / -0

The tendency of a body to resist acceleration is called:

A
Force

B
Retardation

C
Inertia

D
mass

Solution

Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. It is the tendency of objects to keep moving in a straight line at constant velocity.
Question 10
1 / -0

What kind of force acting on an object brings it in motion?

A
internal

B
external

C
null force

D
None of the above

Solution

from Newton's first law we know that only a force can change the state of motion of an object. But if the force is internal then it has no role in the change in the state of motion. It is an external force that causes a change in the state of motion.

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Re-Attempt Weekly Quiz Competition

Forces and Laws of Motion Test - 20

Result

Forces and Laws of Motion Test - 20

Score

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SHARING IS CARING

Question 1

defines the force qualitatively

defines the force quantitatively

explains the way the force acts on a body

gives the direction of force

Solution

Question 2

size of the body

shape of the body

mass of the body

none of these

Solution

Question 3

$$F=\dfrac{m}{g}$$

$$F=mg$$

$$F=ma$$

$$F=\dfrac{m}{a}$$

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

yes, zero

no, zero

yes, positive

no, negative

Solution

Question 6

law of inertia.

Newton's second law of motion

Newton's first law of motion

Newton's third law of motion

Solution

Question 7

$$v=u+at$$

$$F=ma$$

$$F=m/a$$

$$S=ut+(1/2)at^2$$

Solution

Question 8

$$5$$ $${ ms }^{ -2 }$$

$$50$$ $${ ms }^{ -2 }$$

$$2$$ $${ ms }^{ -2 }$$

$$2.5$$ $${ ms }^{ -2 }$$

Solution

Question 9

Force

Retardation

Inertia

mass

Solution

Question 10

internal

external

null force

None of the above

Solution

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