Answer in brief :
(a) What are the effects of a force applied to an object?
(b) Name the different types of force.
(c) How does gravity affect the motion of an object that has been thrown?
(d) Name devices that make use of magnetic force.
(e) Explain the advantages and disadvantages of friction.
(f) What materials would you use to obtain static electric force?
Answer in brief :
(a) What are the effects of a force applied to an object?
(b) Name the different types of force.
(c) How does gravity affect the motion of an object that has been thrown?
(d) Name devices that make use of magnetic force.
(e) Explain the advantages and disadvantages of friction.
(f) What materials would you use to obtain static electric force?
(a) The effects of a force applied to an object are:
• It can move a body from rest.
• It can bring a moving body to rest.
• It can change the direction of a moving body.
• It can change the speed of a moving body.
• It can change the shape of a body.
• It can change the size of a body.
(b) The different types of forces are muscular force, mechanical force, gravitational force, magnetic force, electric force and frictional force.
(c) As we know, the Earth pulls everything towards itself. When an object is thrown with a particular speed, its motion is affected by the gravity. So, the motion of the object in an upward direction decreases gradually and becomes zero at a particular height. After this it falls under the influence of gravity and its motion increases continuously.
(d) Devices such as a magnetic train, electric bell or radio make use of magnetic force.
(e) Friction has many advantages:
(i) We are able to walk because of friction. We find it very difficult to walk on an oily surface. This is because friction between our feet and the ground on an oily surface becomes so little that we cannot move forward.
(ii) We are able to write because of friction present between the paper and the tip of a pen.
(iii) We are able to drive automobiles due to friction between the tyres and the ground. Without friction, it would be impossible to start or stop any vehicle.
(iv) Friction is necessary to hold a glass of water. Due to the friction present between our fingers and the outer surface of the glass, we are able to grip the glass of water. If there was no friction present, it would not be possible to hold it.
Disadvantages of friction are:
(i) Machine parts wear out and need lubrication after a period of time due to the friction present between them.
(ii) Friction also produces heat in machines, when their parts are rubbed against each other. This can lead to overheating of the machine, which may lead to the damage of parts.
(iii) Tyres or soles of our shoes wear out because of friction. For this reason, we need to change our shoes after a period of time.
(iv) To overcome excess friction in air, a lot of fuel is wasted in cars and airplanes. Therefore, cars and airplanes are streamlined and given a unique shape to reduce friction.
(f) Materials used to obtain static electric force include a comb or a pen made up of dry hair or plastic.
(a) The effects of a force applied to an object are:
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• It can move a body from rest. |
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• It can bring a moving body to rest. |
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• It can change the direction of a moving body. |
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• It can change the speed of a moving body. |
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• It can change the shape of a body. |
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• It can change the size of a body. |
(b) The different types of forces are muscular force, mechanical force, gravitational force, magnetic force, electric force and frictional force.
(c) As we know, the Earth pulls everything towards itself. When an object is thrown with a particular speed, its motion is affected by the gravity. So, the motion of the object in an upward direction decreases gradually and becomes zero at a particular height. After this it falls under the influence of gravity and its motion increases continuously.
(d) Devices such as a magnetic train, electric bell or radio make use of magnetic force.
(e) Friction has many advantages:
(i) We are able to walk because of friction. We find it very difficult to walk on an oily surface. This is because friction between our feet and the ground on an oily surface becomes so little that we cannot move forward.
(ii) We are able to write because of friction present between the paper and the tip of a pen.
(iii) We are able to drive automobiles due to friction between the tyres and the ground. Without friction, it would be impossible to start or stop any vehicle.
(iv) Friction is necessary to hold a glass of water. Due to the friction present between our fingers and the outer surface of the glass, we are able to grip the glass of water. If there was no friction present, it would not be possible to hold it.
Disadvantages of friction are:
(i) Machine parts wear out and need lubrication after a period of time due to the friction present between them.
(ii) Friction also produces heat in machines, when their parts are rubbed against each other. This can lead to overheating of the machine, which may lead to the damage of parts.
(iii) Tyres or soles of our shoes wear out because of friction. For this reason, we need to change our shoes after a period of time.
(iv) To overcome excess friction in air, a lot of fuel is wasted in cars and airplanes. Therefore, cars and airplanes are streamlined and given a unique shape to reduce friction.
(f) Materials used to obtain static electric force include a comb or a pen made up of dry hair or plastic.
