Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 18

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Question 1
1 / -0

When a body is stationary, then :

A
There is no force acting on it.

B
The body is in vacuum.

C
The forces acting on it is not in contact with it.

D
The net forces acting on it balances each other.

Solution

Body is stationary means summation of all forces acting on it is zero.
So, $$ \sum F = 0 $$
So, option D is correct.
Question 2
1 / -0

Inertia of a body has direct dependence on :

A
Velocity

B
Volume

C
Mass

D
Density

Solution

The inertia of a body is a measure of, its resistance to a change in the state of its motion/rest. It is solely dependent on the mass of the object. Greater the mass of a body , greater is the tendency to resist a change in its state of motion/rest.
Question 3
1 / -0

A man getting down from a running bus falls forward :

A
as the forward movement of bus tries to pull the man forward

B
due to inertia the upper part of the body moves in the forward direction while feet come to the rest as soon as they touch the road

C
as he leans forward as a matter of habit

D
due to the combination effect of all the three factors stated in $$(A),(B)$$ and $$(C)$$
Solution
Hint: Due to inertia, the body in motion stays in motion and the body in rest remains stationary unless it is affected by an external force.

Explanation:
- According to Newton’s first law of motion, the body in motion stays in motion unless it is affected by an external force.
- The inertia of a body is the tendency of the body to remain in motion, even when the applied force on the body is removed.
- The person in the bus moves in the same direction of the motion of the bus. When the person steps out of the bus, his feet do not move but his upper body moves in the direction of the bus due to inertia of motion.
Hence, a man getting down from a running bus falls forward due to inertia the upper part of the body moves in the forward direction while feet come to the rest as soon as they touch the road.
Correct Option: B
Question 4
1 / -0

A $$60\ kg$$ man pushes a $$40\ kg$$ man by a force of $$60\ N$$. The $$40\ kg$$ man has pushed the other man with a force of:

A
$$40\ N$$

B
$$0$$

C
$$60\ N$$

D
$$20\ N$$

Solution

Newton's third law: To every action, there is an equal and opposite reaction. So when $$60\ kg$$ man exerts a force of $$ 60\ N$$ on $$40\ kg$$ man, $$40\ kg$$ man also exerts the same force of $$60\ N$$ on the $$60\ kg$$ man.
Question 5
1 / -0

Which of the following is NOT attributable to application of force?

A
Rowing of a boat

B
Bursting of a balloon while blowing

C
Pedaling a cycle

D
Catching a moving cricket ball

Solution

Bursting a balloon while blowing is not attributable to application of force.
Question 6
1 / -0

When we kick a stone, we get hurt. Due to which one of the following properties does it happens?

A
velocity

B
momentum

C
inertia

D
reaction forces

Solution

Newton third law states, every action has equal and opposite reaction, When we kick the stone, the stone exerts an equal and opposite force on the leg which hurts us. This force is the reaction force.
Question 7
1 / -0

A man is standing on a platform of a balance and takes a quick step, then his weight:

A
decreases

B
increases

C
remains unchanged

D
first increases and then decreases

Solution

When the man takes a quick step, he will apply more force on the platform than when he just stands on the platform. So, the balance reading will first increase and then decrease.
Question 8
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 9
1 / -0

A lead block is suspended from your hand by a string. The reaction due to the force of gravity on the block is the force exerted by :

A
The string on the block

B
The block on the string

C
The string on the hand

D
The block on Earth

Solution

By law of Gravitation, If the Earth pulls the body with gravitational force F, body pulls the Earth with same force F.
So, reaction of force on block due to the Earth is force on Earth due to the block.
Question 10
1 / -0

A car travels towards the east with a certain constant velocity. The direction of net force on the car is

A
towards east

B
towards west

C
towards up

D
Zero

Solution

From Newton's second law we know that,
$$ F = ma$$, where $$F$$ is the force and $$a$$ is the acceleration.
Again, acceleration $$a$$ is the rate of change of velocity.
As velocity is constant,$$ \ a = 0$$
So, $$ F= 0$$
Option D is correct.

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Forces and Laws of Motion Test - 18

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Forces and Laws of Motion Test - 18

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Question 1

There is no force acting on it.

The body is in vacuum.

The forces acting on it is not in contact with it.

The net forces acting on it balances each other.

Solution

Question 2

Velocity

Volume

Mass

Density

Solution

Question 3

as the forward movement of bus tries to pull the man forward

due to inertia the upper part of the body moves in the forward direction while feet come to the rest as soon as they touch the road

as he leans forward as a matter of habit

due to the combination effect of all the three factors stated in $$(A),(B)$$ and $$(C)$$

Solution

Question 4

$$40\ N$$

$$0$$

$$60\ N$$

$$20\ N$$

Solution

Question 5

Rowing of a boat

Bursting of a balloon while blowing

Pedaling a cycle

Catching a moving cricket ball

Solution

Question 6

velocity

momentum

inertia

reaction forces

Solution

Question 7

decreases

increases

remains unchanged

first increases and then decreases

Solution

Question 8

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 9

The string on the block

The block on the string

The string on the hand

The block on Earth

Solution

Question 10

towards east

towards west

towards up

Zero

Solution

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