Free Force and Pressure 02 Practice Test - 8th Grade 

Question 1

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

A. True
B. False

SOLUTION

Solution : B

An object continues to be in its state of motion or rest until acted upon by an external force. A body changes its state of motion when a non-zero net force is acting on it.

Question 2

Which of the following are non-contact forces?

A.

Electrostatic force

B.

Magnetic force

C.

Gravitational force

D.

Frictional force

SOLUTION

Solution : A, B, and C

The force that can act between two bodies without being in physical contact with each other is called non-contact force. Gravitational, magnetic and electrostatic forces are non-contact forces. Friction can act only when two surfaces are in contact and hence is a contact force.

Question 3

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

A. Weak nuclear force
B.

Strong nuclear force

C. Electrostatic force
D. Magnetic force

SOLUTION

Solution : C

Electrostatic force is the force which acts between charged particles at rest. This force can be repulsive or attractive in nature.

Question 4

Which of the following forces is responsible for the raindrops falling downwards?

A.

Electrostatic force

B.

Magnetic force

C.

Gravitational force

D.

Frictional force

SOLUTION

Solution : C

Water droplets in clouds which eventually form rain have mass. Therefore, they are pulled towards the Earth by the gravitational force of Earth.

Question 5

Gravitational force exists between two persons standing next to each other.

A.

True

B.

False

SOLUTION

Solution : A

Every object in the universe that has mass exerts a gravitational force on every other object having mass. Thus, the given statement is true.

Question 6

A force of 5 N is applied on a body over a surface area of 5 m2. Calculate the pressure applied on the surface.

A.

2 Pa

B.

3 Pa

C.

5 Pa

D.

1 Pa

SOLUTION

Solution : D

Given:
Force on the body F=5 N
Surface area of the body  A=5 m2
Now, pressure applied on the body  P=FA
 P=5 N5 m2=1 Nm−2=1 Pa
Pressure applied on the body =1 Pa

Question 7

A sharp knife cuts better than a blunt knife. Which of the following is the correct reason for this?

A.

A sharp knife has a smaller contact surface area and hence applies less pressure.

B.

A sharp knife is usually made of silver which is a strong metal.

C.

A sharp knife has a smaller contact surface area and hence applies more pressure.

D.

A sharp knife has a larger contact surface area and hence applies more pressure.

SOLUTION

Solution : C

A sharp knife has a lesser contact surface area than a blunt one. Lesser the surface area, greater will be the pressure. So, a sharp knife applies a greater pressure when it is used for cutting. This is why a sharp knife cuts better than a blunt one.

Question 8

The pressure exerted by a liquid depends on:

A. area of the liquid surface
B. shape of the liquid surface
C. height of the liquid column
D. volume of the liquid column

SOLUTION

Solution : 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 9

Which of the following instruments is used to measure atmospheric pressure?

A. Galvanometer
B. Barometer
C. Odometer
D. Thermometer

SOLUTION

Solution : B

Barometers are instruments used to measure atmospheric pressure. A barometer is used by meteorologists to forecast short-term changes in the weather. If the atmospheric pressure falls, storms and rain can be expected.

Question 10

The pressure exerted by the air which is present above us is called:

A. absolute pressure
B. atmospheric pressure
C. gauge pressure
D. fluid pressure

SOLUTION

Solution : B

Atmospheric pressure is defined as the pressure exerted by the weight of the atmosphere. A barometer can be used to measure atmospheric pressure.
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