# Samacheer Kalvi Class 8 Science Unit 2 Force and Pressure Solutions

## Samacheer Kalvi Class 8 Science Unit 2 Force and Pressure Solutions

Welcome to NCTB Solutions. Here with this post we are going to help 8th class students by providing Solutions for Samacheer Kalvi Class 8 Science Unit 2 Force and Pressure. Here students can easily find all the solved solution for Force and Pressure Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 2 Force and Pressure exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.

#### Unit 2 Force and Pressure Exercise Questions Solutions :

(I) Choose the best answer :

(1) If we apply force against the direction of motion of the body, then the body will

(a) stop moving

(b) move with an increased speed

(c) move with a decreased speed

(d) move in a different direction

Answer :

Correct Option → (b)

If we apply force against the direction of motion of the body, then the body will Move with an increased speed.

(2) Pressure exerted by a liquid is increased by

(a) the density of the liquid

(b) the height of the liquid column

(c) Both a and b

(d) None of the above

Answer :

Correct Option → (a)

Pressure exerted by a liquid is increased by The density of the liquid.

(3) Unit of pressure is

(a) Pascal

(b) Nm2

(c) Poise

(d) Both a and b

Answer :

Correct Option → (a)

Unit of pressure is Pascal.

(4) The value of the atmospheric pressure at sea level is

(a) 76 cm of mercury column

(b) 760 cm of mercury column

(c) 176 cm of mercury column

(d) 7.6 cm of mercury column

Answer :

Correct Option → (a)

The value of the atmospheric pressure at sea level is 76 cm of mercury column.

(5) Pascal’s law is used in

(a) hydraulic lift

(b) brake system

(c) pressing heavy bundles

(d) All the above

Answer :

Correct Option → (d)

Pascal law is used in all of the above things

E.g. Hydraulic lift, Brake system, Pressing heavy bundles etc.

(6) Which of the following liquids has more viscosity?

(a) Grease

(b) Water

(c) Coconut oil

(d) Ghee

Answer :

Correct Option → (a)

Grease is a liquid that has a high viscosity in the following liquids.

(7) The unit of viscosity is

(a) Nm2

(b) poise

(c) kgms–1

(d) No unit

Answer :

Correct Option → (b)

The unit of viscosity is Poise.

(II) Fill in the blanks.

(1) The pressure of a liquid column __ with the depth of the column.

(2) Hydraulic lift works under the principle of __

(3) The property of __ of a liquid surface enables the water droplets to move upward in plants.

(4) A simple barometer was first constructed by __

Answer :

(1) → Increases

(2) → Pascal’s law

(3) → Surface tension

(4) → Torricelli

(III) State true or false. If false, correct the statement.

(1) Force acting on a given area is called pressure.

(2) A moving body comes to rest due to friction alone.

(3) A body will sink if the weight of the body is greater than the buoyant force.

(4) One atmosphere is equivalent to 1,00,000 newton force acting on one square metre.

(5) Rolling friction is slightly greater than the sliding friction.

(6) Friction is the only reason for the loss of energy.

(7) Liquid pressure decreases with the decrease of depth.

(8) Viscosity depends on the pressure of a liquid.

Answer :

(1) → True,

But per unit area called pressure.

(2) → True

(3) → True

(4) → True

(5) → False,

Because, Rolling friction is slightly smaller than the sliding friction.

(6) → True

(7) → True

(8) → True

(VIII) Answer very briefly :

(1) Give two examples to verify that a force changes the shape of a body.

Answer :

Stretching of rubber band and pressing the rubber ball by hand this are two examples of force applying on the objects then objects change their shape.

(3) How do you feel when you touch a nail immediately after it is hammered into a wooden plank? Why?

Answer :

After hammered into a wooden plank nail feel hot or warm, Nail became hot or warm because of friction.

(4) How does the friction arise between the surfaces of two bodies in relative motion?

Answer :

The friction arises when we walk on a road. The friction between footwear and the ground help us to walk without slipping this is because friction relative two bodies in a motion.

(5) Name two instruments which help to measure the pressure of a fluid.

Answer :

Barometer and Manometer.

(6) Define one atmosphere.

Answer :

Pressure exerted by the mercury column is considered as the pressure of magnitude is known as one atmosphere.

(7) Why are heavy bags provided with broad straps?

Answer :

Heavy bags are provided with broad straps because, To increasing the surface area on which force is act. due to this pressure is decreases and bag become less weight to carry.

(8) How does surface tension help a plant?

Answer :

In plants xylem tissues are very narrow vessels present in plants water molecules are absorbed by roots and these vessels help the water to rise upward due to capillary action which is caused by the surface tension. This way surface tension help a plant.

(9) Which has greater viscosity, oil or honey? Why?

Answer :

Honey has greater viscosity than oil.

(IX) Answer briefly :

(1) Define friction. Give two examples of the utility of friction in day to day life.

Answer :

The force is produced due to the geometrical dissimilarities of the surface of the bodies which are in relative motion are known as friction. For example- walking on roads, walking on sliding floor with wearing shoes etc.

(2) Mention any three ways of minimising friction.

Answer :

We can minimizing friction in this three ways mentioned in below:

(1) Using lubricants we can decreases the friction

(2) Using ball bearing reduce the friction

(3) Using or making surface more smooth

(4) Why is a ball bearing used in a cycle hub?

Answer :

Ball bearing is used in a cycle hub because to reduce rotational friction and lead shots ball bearing is used.

(X) Answer in detail :

(1) Friction is a necessary evil – Explain.

Answer :

Friction is necessary for our day to day activities. it desirable in most of the situation of our daily life like we can hold objects in our hands due to friction, we can walk on road because friction is there, we can easily applies breaks because friction is present, we can write on a paper with pen easily because friction is present means without a friction we cannot do things properly although friction have some of disadvantages like friction produce heat it causes physical damage to machine but though friction makes our life easy it has some negative effects therefore friction called as necessary evil.

(2) Give the different types of friction and explain each with an example.

Answer :

There are following different types of frictions: –

(a) Static friction :- the friction experienced by the bodies which are at rest is called static friction. For eg- all the objects are rigidly placed to be at rest on the earth.

(b) Kinetic friction :- the friction existing during the motion of bodies is called kinetic friction. It is further having two types –

(c) Sliding friction :- when a bodies slides over the surface of another body the friction acting between the surfaces in contact is called sliding friction.

(d) Rolling friction :- when a body rolls over another surface the friction acting between surfaces in contact is called rolling friction.

(3) Describe an experiment to prove that friction depends on the nature of a surface.

Answer :

Consider a vehicle or cycle. When the cycle travels on rough surface it face difficulty to travel on it but similarly when cycle travel on the smooth surface it travels easily and fast means moving of an object on rough surface is difficult than smooth surface it is because friction varies between the surfaces means friction depends on the nature of the surface.

(5) Describe an experiment to prove that the pressure in a liquid increases with depth.

Answer :

Take a glass tube that is open at both ends. Fix a rubber balloon at the lower end of the tube. Now pour the some water into the tube when we observe balloon we can see the balloon starts bulging outwards now pour again some water into tube again balloon bulging more. From this experiment it is clear that the pressure in a liquid increases with the depth.

(XI) Higher Order Thinking Questions :

(1) Why is it not advisable to use a fountain pen while travelling in an aeroplane?

Answer :

While travelling in an aeroplane it is not advisable to use a fountain pen because, in the aeroplane the pressure is changes and it also affects on fountain pen and it may cause leakage through pen therefore it is advisable to not use fountain pen in an aeroplane.

(2) Is there any possibility of making a special device to measure the magnitude of friction directly?

Answer :

Yes, it is possible to make a special device to measure the magnitude of friction directly.

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Updated: July 31, 2023 — 2:07 pm