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

8th Grade > Physics

FORCE AND PRESSURE MCQs

Total Questions : 56 | Page 1 of 6 pages

Question 1. A balloon inflates when air is pumped into it. Which of the following conclusions can be derived from this?

Gases exert pressure.
Gases don't exert pressure.
Gases don't have any mass.
Gases are heavier than solids.

Discuss Question

Answer: Option A. -> Gases exert pressure.
:
A
Gases exert pressure on the walls of the container they are stored in. This pressure changes the shape of the balloon causing it to inflate.

Question 2. Magnetic and electrostatic forces are contact forces.

True
False

Discuss Question

Answer: Option B. -> False
:
B
A contact forces requires physical contact between bodies for the force to act. Magnetic and electrostatic forces can be applied on a body without actually touching it. Thus, the given statement is false.

Question 3. 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)}

F = P \times A

.
So, for the same amount of pressure P,if we increase the surface area Aof an object,force experienced by thatobject is increased.

Question 4. The reason we are not crushed under the weight of air is that the pressure inside our body is equal to the atmospheric pressure.

True
False

Discuss Question

Answer: Option A. -> True
:
A
The pressure exerted by the atmosphere iscalled atmospheric pressure. Inside the body, the flowing blood and body fluids createa pressure which counters the effect of atmospheric pressure. Therefore, we don't feel atmospheric pressure and arenot crushed by it.

Question 5. A force applied on a body always bring a change in its state of motion.

True
False

Discuss Question

Answer: Option B. -> False
:
B
An object continues to be in its state of motion or rest until acted upon by an external force. Abody changes its state of motion when a non-zero net force is acting on it.

Question 6. The pressure exerted by a liquid depends on:

area of the liquid surface
shape of the liquid surface
height of the liquid column
volume of the liquid column

Discuss Question

Answer: Option C. -> height of the liquid column
:
C
The pressure exerted by a liquid depends on:

density of the liquid

acceleration due to gravity

height of the liquid column

It doesn't depend on area or shape of the liquid surface; nor on volume of the liquid.

Question 7. What is the force which acts between charged particles at rest known as?

Weak nuclear force
Strong nuclear force
Electrostatic force
Magnetic force

Discuss Question

Answer: Option C. -> Electrostatic force
:
C
Electrostatic force is the force which acts between charged particles at rest. This force canbe repulsive or attractive in nature.

Question 8. A force of

5 N

is applied on a body over a surface area of 5

m^{2}

. Calculate the pressure applied on the surface.

2 Pa
3 Pa
5 Pa
1 Pa

Discuss Question

Answer: Option D. -> 1 Pa
:
D
Given:
Force on the body

F = 5 N

Surface area of the body

A = 5 m^{2}

Now, pressure applied on the body

P = \frac{F}{A}

P = \frac{5 N}{5 m^{2}} = 1 N m^{- 2} = 1 P a

Pressure applied on thebody

= 1 P a

Question 9. When an archer pulls the string of a bow, which of the following force is in play?

Muscular force
Nuclear force
Gravitational force
Magnetic force

Discuss Question

Answer: Option A. -> Muscular force
:
A
The archer stretches the string of the bow by applying muscular force. In the process, the shape of the bow changes.

Question 10. If the net force on an object is acting in the direction of its motion, its speed decreases.

True
False
Size of the object
Shape of the object

Discuss Question

Answer: Option B. -> False
:
B
If a net force isapplied on anobject moving with some speed,in the direction of its motion, its speed increases. For example, for a ball dropped from a roof, direction of motion and direction of force are in the downward direction. The speed of the ball keeps increasing until it hits the ground.