Telangana SCERT Class 8 Physical Science Chapter 1 Solution – Force. Here in this post we provides Class 8 Physical Science Force Telangana State Board Solution. Telangana State Board English Class VIII Medium Students can download this Solution to Solve out Improve Your Learning Questions and Answers.
Telanagana State Board Class 8 Physical Science Chapter 1 Force Solution:
(1) What is a force? What changes can be produced by a Force?
Ans: – Force is a push or a pull. Such actions like picking, squeezing, twisting, stretching, lowering, lifting etc…. all are done by force. It causes a change in the state of an object.
Changes which can be produced by a force are-
(i) Force can change of the state of motion of an object and its direction.
(ii) Force can change the shape, size, of an object.
(iii) A force can change an object with or without being in contact with it.
(iv) Force can increase or decrease the speed of motion.
(2) Give two examples each for a contact force and a force at a distance.
Example of contact force: –
(i) Pushing a chair
(ii) Writing with pen or Pencil.
Examples of force at a distance: –
(i) Falling an apple from tree.
(ii) The needle of the compass change its direction without any physical contact with the bar magnet.
(3) Explain Gravitational Force by giving a suitable example.
Ans: – If an object is thrown upwards, there exists a force which pulls it down towards the earth, because of this it falls down to the ground. We call this force as a gravitational force.
The force of gravity is not just due to the attraction of the Earth. It is a force of attraction that exists between any two bodies everywhere in the universe.
When we throw a ball high into the sky, it comes down with its speed (velocity). And does not pull earth towards it as it has a very less mass as compared to the earth and as we know that gravity depends on mass and distance. So as earths mass is much greater than the ball, so it pulls the ball towards it, rather than being pulled by the ball.
(4) Draw and explain a free body diagram (FBD) to show all the forces acting on a car?
Ans: – The diagram showing all the forces acting on an object at a particular instant is called free body Diagram Known as FBD.
Examples: – A car is moving with a non uniform speed along a road.
The forces acting on the car are shown in the FBD (Free body diagram).
They are –
Force applied by the engine = F
Friction applied by road = F
Normal Forces are N1 and N2
Net force along X –axis or direction F net x = f – F
Net force along y – axis or direction F net, y = N1 + N2 – W
(5) Why do tools meant for cutting always have sharp edges?
Ans: – The cutting edges of tools like knives, blades, etc have a sharp edge to cut the things easily.
Because sharp edges have less area on which the force is applied, so it helps in applying high pressure.
Application of concepts
(1) How can you differentiate between a contact force and a force at a distance?
Ans: – The force which occurs by a direct physical contact between two interacting objects is known as contact force.
The force which occurs without any physical contact between two objects is known as a force at a distance or fields force.
Example of force at a distance is – magnetic force applied by a magnet.
In contact force, force is applied to a body by another body.
In a force at a distance is a force which on an object without coming any body contact with it.
(2) Find the net forces from the following diagrams.
And: – Net force = F1 (-F2)
= F1 – F2
(a) Net force
= (10 + 8) – 12
= 18 – 12
= 6 N
(4) The surface area of an object is 20 m2 and a force of 10 N is applied on it, then what is the pressure?
Ans: – The force acting perpendicularly on unit area of a surface is called pressure
So, Pressure = Force/Area
Here, Force = 10 N,
Surface area of an object = 20 m2
Pressure = 10 N/ 20 m2
= (10/20) N/m2
= 0.5 N/m2
(5) How do you appreciate the role of friction in facilitating our various activities?
Ans: – Friction is the resistance to the movement of a body over the surface of another body. The direction of friction is always opposite to the direction of motion relative to the surface.
So, we can easily say that we walk easily because of friction. If there would be no friction we would slip and full down.
We can write, when we do it a pen or pencil or chalk, it is because if friction, but friction hold these object together but sometimes friction can be harmful in such cases like rubbing surface in machines, but in that case it can cause fines.
So we can say that friction in used in our everyday activities like writing, walking, playing etc.
Higher Order Thinking Questions
(1) If you push a heavy box which is rest, you must exert some force to start its motion. However once the box is sliding you apply a lesser force to maintain that motion. Why?
Ans: – Here when the box is at rest, there is static friction. But when it is sliding, there is sliding friction
We know that –
Static Friction -> Sliding friction means sliding friction is less than statistics friction.
So when the box is in sliding. We apply a lesser force to maintain that motion.
(2) How do you increase the pressure by keeping?
(a) Area unchanged
(b) Force unchanged
Ans: – Pressure depends on force and area of surface.
P = F/A
So to increase pressure force should be increased and also if pressure decreased the force also decreased.
When the pressure is increased the area decreased and when the pressure is decreased then area increases.
So, when the force is increased the pressure will also increase but keeping the area unchanged. Means if you want to increase pressure while keeping the area unchanged, you have to change force.
If we can increase the pressure by keeping the force unchanged then increased temperature.
(3) Imagine that friction disappeared from the earth. What will happen? Explain
Ans: – If the friction disappeared from the earth, we could not write walk, play and also we could not do anything if there is no friction. If there is no friction, our whole body system will not work properly. People will not be able to control cars, if there is no friction. So as results, a lot of accidents occur.
If there will be no friction, then there is no sound, because friction helps in transfer of sound.
Multiple Choice Questions
(1) Hoisting a flag is related to
Ans: – (c) push and pull
(2) A person is pulling water from well. Which type of force it is
Ans: – (a) Muscular force
(3) The force that a solid surface exerts on any object in the normal
Ans: – (b) Normal Force
(4) Let the forces F1 and F2 act on the table in opposite directions,
Ans: – (a) F1 – F2
(5) A situation for effect of force leads to a permanent change in shape of object is
Ans: – (d) Breaking glass