[PDF] Extra Questions for Class 8 Science Chapter 11 Force and Pressure
Here we are providing extra questions for CBSE Class 8 Science Chapter 11 Force and Pressure. In the pursuit of a comprehensive understanding of CBSE Class 8 Science Chapter 11 “Force and Pressure,” practicing extra questions emerges as a valuable strategy. Students are suggested to go through each and every question for better concept coverage.
Table of Contents
Very Short Answer Type Questions
Q.1 What is force?
Ans. A push or a pull on an object is called force.
Q.2 What is the requirement for a force to come into play?
Ans. Interaction between two objects is required for force to come into play.
Q.3 What is the resultant force when two forces act in same direction?
Ans. Forces applied on an object in the same direction add to one another.
Q.4 What will be the resultant force when two forces act in opposite directions on an object?
Ans. When two forces act in opposite directions on an object then the net force will be the difference between two forces.
Q.5 What happens in a tug of war when two teams pull equally hard?
Ans. When two teams pull equally hard then the rope does not move in any direction.
Q.6 When does the net force become zero?
Ans. When two forces acting on an object in opposite directions are equal then the net force becomes zero.
Q. 7 What is muscular force?
Ans. The force resulting due to the action of muscles is known as muscular force.
Q.8 Give two examples of contact forces.
Ans. (i) Muscular force (ii) Force of friction
Q.9 What are non-contact forces?
Ans. The forces acting from a distance without making contact are called non-contact forces.
Q.10 Give an example of a non-contact force.
Ans. Magnetic force.
Q.11 What is magnetic force?
Ans. The force exerted by a magnet on any magnetic object is called magnetic force.
Q.12 What are the interaction of poles of two magnets?
Ans. (i) Like poles repel each other. (ii) Unlike poles attract each other.
Q.13 What kind of force is an electrostatic force?
Ans. It is non-contact force.
Q.14 What is gravitational force?
Ans. The force by which earth or any other object attracts objects towards itself is called the gravitational force.
Q.15 What do you mean by pressure?
Ans. The force acting on a unit area of a surface is called pressure.
Pressure = Force / Area
Q.16 What is atmosphere?
Ans. The envelop of air around us is called atmosphere.
Q.17 What is atmospheric pressure?
Ans. The pressure exerted by the air is known as atmospheric pressure.
Short Answer Type Questions
Q. 18 What is a force? Explain with the help of some examples.
Ans. Force is a pull or push of the objects. The action like, pushing, pulling, picking, hitting, lifting, running and bending are the examples of force. Moving or stopping of a body, changing shape and direction of motion of objects are various actions which show force in play.
Q.19 What is the effect of force on the shape of an object?
Ans. A force can change or try to change the shape of an object. When a force is applied on an object then change in shape may take place. It may be smaller or greater. At last we can say that the application of force on an object may change its shape.
Q.20 Explain contact and non-contact forces.
Ans. Contact forces: The forces which come in action only when two objects come in the contact with each other are called contact forces. Muscular force and force of friction are the examples of contact forces.
Non-contact forces: The forces which come in the action without any contact with one another are
called non-contact forces. Electrostatic and magnetic forces are the examples of non-contact forces.
Q.21 What is muscular force? Why is it called contact force?
Ans. The force resulting due to the action of muscles is known as the muscular force. Muscular force is called contact force because it comes in action when two bodies come in contact with each other.
Q.22 What do you understand about the force of friction?
Ans. The force which always acts on all the moving objects and whose direction is always opposite to the direction of motion is called force of friction. Since the force of friction arises due to contact between surfaces, it is also called contact force.
Q.23 What is electrostatic force? Why is it called non-contact force?
Ans. The force exerted by a charged body on another charged or uncharged body is called electrostatic force. This force comes into play even when the bodies are not in contact, so it is called non-contact force.
Q.24 Explain force of gravity.
Ans. Objects or the things fall towards the earth because the earth pulls them. This force is called force of gravity or the force due to gravitation. It is an attractive force. This force acts on all objects.
Q.25 What is pressure? What happens to the pressure when area on which it is applied increases?
Ans. The force acting on a unit area of a surface is called pressure.
Pressure = Force/Area on which it acts.
The pressure is inversely proportional to the area on which force is applied. As the area on which force is applied is increased, the pressure decreases. We can say that pressure increases with decrease
in area.
Q.26 We observe that the wheels of buses and trucks are broader than the wheels of car or scooters. Why?
Ans. The buses and trucks are heavy and require to exert less pressure. We know that pressure decreases as area of contact increases, so the tyres are broadened so that they exert less pressure on earth and move easily. If they exert more pressure, they will sink in earth. The scooters and cars have less wide wheels because they need more pressure for gripping.
Q.27 Why do mountaineers suffer from nose bleeding at high altitudes?
Ans. The atmospheric pressure decreases with high altitude. Since the pressure of the blood inside: the body is high, the nose starts bleeding.
Q.28 Why is it easier to hammer a sharp nail into wood than a blunt one?
Ans. Pressure = force / area.
Therefore, when we hammer a sharp nail, force acts on a smaller area, and it exerts more pressure on
the nail.
Q.29 How would pressure change if
(a) area is doubled keeping force constant
(b) force is doubled keeping area constant?
Ans. (a) If area is doubled keeping the force constant, then pressure becomes half.
(b) If force is doubled keeping area constant, then pressure becomes double.
Q.30 Why does a boat come to rest when we stop rowing it?
Ans. The boat comes to rest when we stop rowing it due to the force of friction acting between the surface of water and the boat.
Q.31 Give reasons for the following:
(a) The skiers use flat and broad skis
(b) Deep sea divers wear special suits.
Ans. (a) The skiers use flat and broad skis to ski on the snow. The larger surface of skis reduces pressure on snow and helps them to slide instead of sinking.
(b) Deep sea divers wear special suits, because the pressure of water increases with depth. The
increased pressure may hurt the body of divers.
Q.32 How does the medicine enter a dropper?
Ans. When the dropper is pressed, the air inside the dropper is driven out. The pressure inside the dropper decreases and the medicine rushes inside the dropper.
Long Answer Type Questions
Q.33 What are contact forces? State different contact forces.
Ans. The forces which come in to play only when two objects come in contact with each other are called contact forces.
Some contact forces are:
(i) Muscular force: The forces resulting due the action of muscles are known as muscular
forces. Muscular force is a contact force because it comes in play when two bodies come in
contact with each other
(ii) Force of friction: When a body is moving, then a force equal and opposite to direction of
motion is exerted on that moving body. This force is called force of friction. It is also a contact
force because it is exerted when two surfaces come in contact with each other.
Q.34 What are non-contact forces? Explain different types of non-contact forces.
Ans. The forces which can be exerted from a distance, without establishing a contact are called non-contact forces. Some non-contact forces are:
(i) Magnetic force: The force exerted by a magnet on other magnet or some other magnetic substances like iron is called magnetic force. Like poles of a magnet repel each other and unlike poles of a magnet attract each other without contact. So it is called non-contact force.
(ii) Electrostatic force: The force exerted by a charged body on other charged or uncharged body is called electrostatic force. Electrostatic force also acts without making a direct contact with other charged or uncharged body. So it is also a non-contact force.
(iii) Force of gravity: Earth pulls every thing or body towards it. The force of attraction exerted by earth on every object is called force of gravity. This is also a non-contact force as it acts from a distance.
Q.35 Prove that the force of friction depends on the nature of the two surfaces in contact.
Ans. Collect the following things: A thick book, nylon cloth, gunny cloth, plastic sheet, jute cloth and sand paper. Place the book on each of the materials and slide it on the floor one by one. If your book slides off the plastic sheet or nylon cloth, use adhesive tape to stick it firmly on the surface of the book.
You will observe that the different materials offer different amounts of resistances to sliding.
This activity shows that force of friction depends on the nature of the surface in contact. In general,
smooth surface offers lesser friction than rough surface.
Significance of Practicing Extra Questions
The significance of practicing extra questions cannot be understated. These questions provide students with opportunities to revisit and apply the knowledge they’ve acquired from the chapter. As they engage with diverse problems, students sharpen their analytical thinking and enhance their ability to approach a range of scenarios related to force and pressure. Moreover, the act of solving extra questions cultivates a sense of confidence in tackling various exam formats and challenges.
CBSE Class 8 Science: Force and Pressure Overview
Let’s take a closer look at what we’ll be exploring in Chapter 11 of CBSE Class 8 Science, titled “Force and Pressure.
“In this chapter, we will learn about something called force – which is a push or pull that can make things move or stop. Imagine pushing a door open or pulling a toy towards you – you’re using force! We will also learn about pressure, which is the amount of force spread over an area. You might have noticed that sharp objects, like pins, create more pressure compared to dull ones.
We’ll discover how forces can change the shape or state of objects, and how pressure plays a role in various everyday situations. From understanding how our muscles work to how liquids flow, this chapter will help us see how forces and pressure are all around us.
Frequently Asked Questions (FAQs)
Q1: What is force?
Force is a push or pull that can make an object move, change its speed, or stop its motion. It can also change the shape of an object.
Q2: How do forces affect motion?
Forces can cause motion by making objects start moving, stop moving, or change direction. They can also change the speed or shape of an object in motion.
Q3: What are contact and non-contact forces?
Contact forces involve direct physical contact between objects, such as pushing a door open. Non-contact forces, on the other hand, act from a distance, like the gravitational pull of the Earth on us.
Q4: How does friction influence movement?
Friction is a force that opposes motion. It can slow down or stop moving objects. For example, when you slide a book across a table, friction between the book and the table’s surface slows it down.
Q5: Can forces change the shape of objects?
Yes, forces can change the shape of objects. For instance, when you squeeze a rubber ball, you’re applying force that changes its shape.
Q6: What is pressure? How is it calculated?
Pressure is the amount of force distributed over a given area. It is calculated by dividing the force applied by the area over which it’s spread. Pressure = Force / Area.
Q7: How does pressure vary in liquids and gases?
Pressure in liquids and gases increases with depth. In a fluid, the pressure at the bottom is higher due to the weight of the fluid above pushing down.
Q8: Why do sharp objects exert more pressure than dull ones?
Sharp objects have a smaller surface area in contact with the object, causing the force to be concentrated over a smaller area. This concentration results in higher pressure.
Q9: How does pressure change as we go deeper underwater?
Pressure increases with depth underwater. The weight of the water above adds more force on an object at greater depths, leading to higher pressure.
Q10: Why is pressure higher at the bottom of a container with fluid?
Pressure increases with depth in a fluid due to the weight of the fluid above. As you move lower in the container, the weight of the fluid above creates more pressure on objects at the bottom.