Force And Pressure(8th Grade > Physics ) Questions and answers for exam Preparation

8th Grade > Physics

FORCE AND PRESSURE MCQs

Total Questions : 56 | Page 4 of 6 pages

When a porter uses a round piece of cloth on his head while carrying luggage, it reduces pressure by increasing the area of contact.

True
False

Discuss Question

Answer: Option A. -> True
:
A

Pressure is inversely proportional to the area of contact. For the same force, more surface area results in lesser pressure.

When a porter uses a round piece of cloth on his head while carrying luggage, the area of contact increases. As a result, pressure decreases.

Question 32.

A $50 N$ force is applied on an area of $2 m^{2}$ . Compute the pressure.

$100 P a$
$0 P a$
$1 P a$
$25 P a$

Discuss Question

Answer: Option D. ->

25 P a

:
D
Given:
Force,

F = 50 N

Area,

A = 2 m^{2}

From definition of pressure

(P)

P = \frac{F}{A}

P = \frac{50}{2} = 25 P a

Question 33.

A block sliding on a horizontal rough surface comes to rest after travelling some distance on it. The force which is responsible for stopping the block is:

gravitational force
magnetic force
electrostatic force
frictional force

Discuss Question

Answer: Option D. -> frictional force
:
D
Friction is a force that opposes relative motion between two surfaces in contact. A body sliding on a horizontal surface stops because the surface on which it slides resists its motion.

Question 34.

Equal amount of pressure is applied on two surfaces with different surface areas. For such a condition, which of the following statement is correct?

Both the surfaces experience the same force.
The surface having more surface area experiences more force.
The surface having less surface area experiences more force.
Both the surfaces experience zero force.

Discuss Question

Answer: Option B. -> The surface having more surface area experiences more force.
:
B

According to formula $P r e s s u r e P = \frac{F o r c e (F)}{A r e a (A)}$
or $F = P \times A$ .
So, for the same amount of pressure P, if we increase the surface area A of an object, force experienced by that object is increased.

Question 35.

Charges are of two types: negative and positive. Like charges repel while unlike charges attract each other.

True
False
shape of rubber bulb
pressure difference

Discuss Question

Answer: Option A. -> True
:
A

Charges are of two types: positive and negative. From the property of charges, we know that, like charges repel while unlike charges attract each other.

Question 36.

When we press the bulb of a dropper with its nozzle inside water, the air present in the bulb escapes in form of bubbles. Once we release pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is driven by_________.

pressure inside the dropper
gravity of Earth
shape of rubber bulb
pressure difference

Discuss Question

Answer: Option D. -> pressure difference
:
D
When we press the bulb of a dropper, the number of air molecules decreases which results in a decrease in pressure inside the dropper nozzle. However, the outside pressure or atmospheric pressure remains the same. Therefore there is a difference in pressure between outside of the nozzle and inside of the nozzle. Since water flows from a region of higher pressure to a region of lower pressure, water rushes to fill inside the dropper.

Question 37.

Which of the following are fundamental forces?

Gravitational force
Frictional force
Strong nuclear force
Electromagnetic force

Discuss Question

Answer: Option D. -> Electromagnetic force
:
A, C, and D

There are four fundamental forces in nature:

Gravitational force

Electromagnetic force

Weak nuclear force

Strong nuclear force

Frictional force is not a fundamental force.

Question 38.

What action is being applied by the character on the rope shown below while hanging upside down?

Push
Pull
Both push and pull
Neither push nor pull

Discuss Question

Answer: Option B. -> Pull
:
B
As we can see, the character is pulling the string downwards, so that he can hang. The string has to be strong enough to support his weight.

Question 39.

Which of the following quantities specify the force acting on an object?

Magnitude of the force
Direction in which the force is acting
Size of the object
Shape of the object

Discuss Question

Answer: Option A. -> Magnitude of the force
:
A and B

Force is a vector quantity which has both magnitude and direction. To define a force accurately, both magnitude and direction of the force must be specified.

Question 40.

A balloon inflates when air is pumped into it. Which of the following conclusions can be derived from this?