# RBSE Solutions for Class 8 Science Chapter 9 Work and Energy

## Rajasthan Board RBSE Class 8 Science Chapter 9 Work and Energy

RBSE Solutions for Class 8 Science ### RBSE Class 8 Science Work and Energy Intext Questions and Answers

Page No 81.

Question 1.

1. Put a ball on floor and push it. i.e. exert force on ball.
2. Push the walls with your hands. In both above activities, which is the object displaced from its one position to another position ?

Ball changes its position from one place lo the other. Here, the ball covers some distance in a particular direction. Distance covered by an object in a particular direction is called displacement.

Page No 98.

Question 2.
An object is pulled firstly to 2m and then for 4m. In which case the work done is more?
More work is done in case of pulling the object to 4m than to 2m because when the displacement is more the work done is also more.

Question 3.
Firstly place two books in cardboard box and pull It 4 meter. Again after full packed with books pull it 4 meter. In both situation displacement Is same.

1. In which situation more force is applied?
2. In which situation more work has to be done?

1. More force is applied in second situation because the weight is more.
2. More work has to be done in second situation because the force is more.

Pages No 99-100.

Question 4.
In the table some actions are given. Write in this table the name of the object who is doing work and name of the object, on which work has to be done.  Page No 103.

Question 5.
In our daily life we see energy conversion from one form into another form. On the basis of your daily analysis, fill the following table.
Table Page No 105.

Question 6.
Find out the location of various power plants – hydro, thermal and atomic power plants in Rajasthan.

1. Hydroelectric Power Plants –
• Jawahar Sagar Bandh – Koia
• Rana Pratap Sagar Bandh – Chittorgarh,
2. Thermal Power Plants –
• Suratgarh – Kota
• Chabra – Dhoulpur, etc.
3. Atomic Power Plants –
4. Rawatbhata – Chittorgarh.

Question 7.
What do you do for save energy? The energy measur enlist.
We use the following methods for the conservation of energy –

1. Use electrical equipments when there is necessity. When there is no person in the room then switch off all electrical equipments.
2. Save fuel by use of solar cooker. advanced gas stove, pressure cooker for cooking purpose. Do not combust wastefully cooking gas. kerosene, stove and sigri.
3. On, stopping or at waiting time, switch off the engine of vehicles and save wasteful use of petrol and diesel. Always service the vehicles at time and always use proper air and oil in vehicles.
4. By the use of solar energy. we can save conventional energy resources.
5. We can conserve conventional sources of energy by use of bio-gas and biotic substances.
6. The technique used in the building should be such that they remain hot in winter and cold in summer. In this way. there will be save of electricity and less use of heater or A.C.
7. Daily utility items are manufactured by use of electricity or other type of energy. Thus we should use them with austerity.
8. There is saving of electricity by use of LED lights in place of bulb or tubelight in home and commercials,

### RBSE Class 8 Science Work and Energy Text Book Questions and Answers

Question 1.
The unit of energy is –
(a) Newton
(b) Kilogram
(c) Joule
(d) Watt
(c) Joule Question 2.
The capacity of doing work is called –
(OR)
The working capacity in things is called –
(a) Power
(b) Force
(c) Momentum
(d) Energy
(d) Energy

Question 3.
One of the following is not fossil fuel –
(a) Petrol
(b) Wood
(c) Natural gas
(d) Diesel
(a) Petrol

Question 4.
Which is the apparatus used to convert electric energy into sound energy –
(a) Electric motor
(b) Electric magnet
(c) Electric heater
(d) Electric bell
(c) Electric heater Fill In the blanks (with suitable words):

1. The energy in objects due lo its motion, is called __________ of an object.
2. The stressing the rubber in sling-shot, the __________ energy stored in it.
3. Electric cell, used in house hold, converts __________ energy into electric energy.
4. Unit of energy is __________

1. Kinetic energy
2. Potential,
3. Chemical
4. Joule

Match the column (A) and column (B): 1. (d)
2. (c)
3. (b)
4. (a)

Question 1.
Define Work?
Work on an object is said to be done when the force acting on it produces displacement in it, in the direction of the applied force. Work = Force x Displacement in the direction of force Thus the product of force and the displacement in the direction of applied force is called work. The SI unit of work is “Joule”.

Question 2.
Which are the things on which work done on the object depend?
Work done on an object depends upon –

1. Displacement
2. Extent of force applied. Question 3.
Give the two-two names of the things which store kinetic energy and potential energy in it on the basis of daily life observation.
Potential energy –

1. Toys having key operation have potential energy.
2. Watch having key operation has potential energy.

Kinetic Energy –

1. Flowing water has kinetic energy.
2. Blowing air or wind has kinetic energy.

Question 4.
how do we define the energy conversation? Explain energy transfer on the basis of three different examples.
Conversion of energy from one form to another form is called energy transformation or energy conversion.
Examples –

1. Electric heater converts electric energy to heat energy.
2. Solar cells convert light energy to electric energy.
3. Electric generators converts mechanical energy to electric energy.

Question 1.
What do you mean by global energy crisis? What are the measures you adopt to resolve the global energy crisis. Describe it in detail.
Energy Crisis – Limited sources of fossil fuels and increasing demand of energy to fulfil energy requirement by the increasing population has resulted in a global crisis, which is known as global energy crisis. Solutions to deal with Global Energy Crisis –

1. Electric appliances should be used when necessary and excessive use of these appliances should be avoided.
2. While cooking solar cookers, pressure cookers. etc. should be used to save fuel. LPG, Kerosene, stove, gas, etc. should not be unnecessarily burnt.
3. While waiting for someone or at red light signals vehicle engines should be put off to save unnecessary consumption of petrol, diesel. Servicing and checking of the vehicle should be done timely and air and oil level should be maintained.
4. By using solar energy we can save traditional fuels.
5. Biodegradable wastes and gobargas can be used as hiogas fuel and we can conserve the depleting sources of fossil fuels.
6. While construction of buildings such type of technique should be used so that they are cold in summers and hot in winters. This way heater and A.C. would be used less and we can save on electricity.
7. In day to day life activities electricity and other forms of energy is used. Hence, they should he used economically and judiciously.
8. LED lights should be used in houses and offices in place of normal bulbs and tubelights as they save on electricîty.

Question 2.
Explain the differences between conventional energy sources and non – conventional energy sources with providing suitable examples. ### RBSE Class 8 Science Work and Energy Important Questions and Answers

Objective Questions:

Question 1.
When the displacement in an object is there than the work done is –
(a) Less
(b) More
(c) Equal
(d) Neither less nor more
(b) More

Question 2.
Work and energy are to each other.
(a) Equivalent
(b) Less
(c) More
(d) None of these
(a) Equivalent Question 3.
Wind energy is used to run –
(a) Wind Mill
(b) Mill
(c) Hydro Mill
(d) Solar Mill
(a) Wind Mill

Question 4.
Energy obtained due to the movement of charges is –
(a) Light energy
(b) Mechanical energy
(c) Electric energy
(d) Atomic energy
(c) Electric energy

Question 5.
Where is the Nuclear Power Station in Rajasthan located ?
(a) Jaipur
(b) Chittor
(c) Udaipur
(d) Rawathhata
(d) Rawathhata Fill in the blanks:

1. The distance traveled by an object in a definite direction is called ……………………. (displacement / energy)
2. The objects possess ……………………. due to their shape or position. (Energy I Force).
3. Two forms of mechanical energy is ……………………. and . (Electric energy, Light energy / Kinetic energy, Potential energy)
4. ……………………. can also be run using atomic energy. (Aeroplane / Submarine).
5. The S.I. unit of both work and energy is …………………….. (Joule / Hertz)

1. displacement
2. Energy
3. Kinetic energy, Potential energy
4. Submarine
5. Joule

State whether the following statements are True or False:

1. The work done on an object does not depends upon it displacement.
2. Work = force x displacement in direction of force.
3. Whether the objects are living or non living, they have the capacity to do work.
4. Potential energy and kinetic energy are together called chemical energy.

1. False
2. True
3. True
4. False

Math the Column –

Question 1.
Match the following correctly: 1. (c)
2. (a)
3. (b)
4. (e)
5. (d)

Question 1.
Energy is transformed in electrical
appliances. What form of energy is used in an electric heater’? What form of energy is transformed in this process.
in an electric heater energy is used in the form of electric energy. In an electric heater electric energy is transformed into heat energy.

Question 2.
What is meant by displacement?
Distance covered by an object in a fixed direction is called displacement. Question 3.
On what factors the work done on an object depends upon?
The factors on which the work done on an object depends upon are –

1. Displacement
2. Magnitude of the force applied on object.

Question 4.
What is the S.l. unit of work?
The S.l. unit of work is “Joule’t.

Question 5.
What is meant by energy?
The capacity to do work is called energy.

Question 6.
Give some examples in which energy is possessed?
Running water, wind, coal, steam. diesel, petrol, electricity, etc. possess energy. Many types of work are carried out with these energies. Question 7.
What is the relation between work and energy?
Work and energy are equivalent to each other.

Question 8.
What is the unit of energy?
The S.J. unit of energy is Joule.

Question 9.
What is mechanical energy?
Mechanical energy is the summation of potential energy and kinetic energy. i.e. Mechanical Energy = Potential Energy + Kinetic Energy

Question 10.
What is kinetic energy?
The energy possessed by a object by virtue of its motion is called kinetic energy.

Question 11.
Give examples of Kinetic Energy.
Examples of kinetic energy are – water, wind, vehicle etc. possessing energy due to their motion.

Question 12.
What is potential energy?
The energy stored in a object by virtue of its position or shape or configuration is called potential energy. Question 13.
Give an example of potential energy.
When a stone in nibber (slingshot) ¡s stretched and thrown then stone perform motion is an example of potential energy.

Question 14.
Give examples of heat energy.
To drive an engine from the heat of coal, to run vehicles using petrol / diesel engine.

Question 15.
Does one form of energy converts into another form? What is it called?
Yes, one form of energy does converts into another form of energy. It is called energy transformation.

Question 16.
What are the conventional sources of energy?
Petrol, diesel, natural gas, coal, etc. fossil fuels and wood etc. are the conventional sources of energy.

Question 17.
What is meant by fossil fuels?
Millions of year ago due to disturbances in the interior of earth, many plants, animals got buried under the earth. After long time due to the excessive pressure and temperature of the earth these plants and animals got converted into petroleum and mineral coal. These are known as fossil fuels.

Question 18.
What are the non conventional sources of energy?
Solar energy, water energy, wind energy, biotic energy, geothermal energy, Sea energy, etc. are the sources of non conventional sources of energy. Question 19.
What is meant by alternative and renewable source of energy?
The non conventional sources of energy are called alternative sources of energy. These sources are used again and again hence they are also called renewable sources of energy.

Question 20.
What is heat energy?
Energy contained in a burning object or heated object is called heat energy.

Question 21.
What is chemical energy?
Energy contained in chemicals like fuel etc. is called chemical energy.

Question 22.
What is electric energy?
Electric energy is the energy which is caused by moving electrical charges.

Question 23.
Define magnetíc energy.
Energy contained in magnetic field is known as magnetic energy. Question 24.
What is sound energy?
Energy contained in sound (vibrations) is called sound energy.

Question 25.
What is atomic energy?
Fusion or division of nucleus provides energy known as nuclear energy.

Question 26.
For electricity generation which energy is used?
For electricity generation kinetic energy of water, heat energy of coal, wind energy and atomic energy is used.

Question 1.
What is work done? Give its unit. Also give an example.
Work – Work is said to be done when the force acting on the body produces displacement in it, in the direction of the force applied. Unit of Work – The international unit of work is “Joule”. Example – Close an empty cardboard carton by putting only two books in it. Now tie it with a rope and pull it 2 metres on the ground. Now again pull it for 4 metres on the ground. Here, an applying force the cartoon displaces from position. Thus work is done. Work = Force x Displacement. Question 2.
What is meant by mechanical energy? What are its type? Give examples of each.
Mechanical Energy – The energy possessed by the objects due to their motion and due to change in their positions is called mechanical energy. It is two types –

1. Kinetic Energy – Energy possessed by the object due to its motion is called kinetic energy. e.g. the working of wind mill due to wind energy.
2. Potential Energy – Energy possessed by an object by virtue of its position or shape or configuration is called potential energy. e.g. rotating the turbine by water falling from a height.

Question 3.
What is energy? Give ¡ts various forms with examples. Also give its unit.
The capacity of doing work by an object is called energy. Examples – Running water, wind, coal, steam, diesel, petrol, electricity, etc. are sources of energy. Forms of Energy – Mechanical energy, heat energy, light energy, magnetic energy, electrical energy. atomic energy, etc. The unit of energy is also “Joule”.

Question 4.
What are the various sources of energy? Explain in short.
Energy basically have Two sources –

1. Conventional or traditional sources of energy – Petrol, diesel, natural gas. coal. fossil fuels, wood used by us are conventional source of energy.
2. Non-conventional – Sun, wind, water, bioinass, nucleal: furnace, geothermal energy, sea energy are the non conventional or alternative sources of energy.

Question 5.
How can energy be conserved?
(OR)
Provide in formation regarding conservation of energy.
Following methods can be adapted for the conservation of energy –

1. Use the electrical equipments when there is its necessity.
2. Save fuel by using solar cooker, advanced gas stove, pressure cooker for cooking purpose.
3. Do not combust wastefully cooking gas, kerosene, stove, etc.
4. On stopping or waiting time, switch off the engines of the vehicles. Always service the vehicle at proper time.
5. Use solar energy maximum.
6. Use biogas, bio energy and biotic substances.
7. Use proper technique in the building or houses so that they remain cool in summer and hot in winter.
8. The LED devices should be used. Question 6.
Give the examples of the following forms of energy.

1. Mechanical energy
2. heat energy
3. chemical energy
4. light energy
5. electrical energy
6. magnetic energy
7. sound energy
8. atomic energy.

1. Mechanical Energy – Water, wind, energy due to motion of vehicle, energy of spring, slingshot and bow, etc.
2. Heat Energy – Driving the engine of a vehicle with the help of petrol or diesel.
3. Chemical Energy – All types of fuels.
4. Light Energy – Production of electricity using solar cells.
5. Electrical Energy – Lighting the bulb, electric fan and electric motor etc.
6. Magnetic Energy – Attraction of an iron rod with magnet.
7. Sound Energy – Sound received from vibrations of musical instrument.
8. Atomic Energy – Production of electricity by atomic (nuclear) furnace.

Question 7.
We see the transformation of energy from one form to another form in our daily life. Write any four such examples.
The change of one form of energy into another form –

1. Conversion of electric energy into light energy. Example – bulb or lube light.
2. Conversion of chemical energy into electric energy, Example – Electric cell.
3. Conversion of electric energy into heat energy, Example – Electric heater.
4. Conversion of mechanical energy into electric energy, Example – Dynamo, generator.

Question 1.
Make a table of various forms of energy and define them briefly providing exam pies. Question 2.
Explain the transformation of energy with the help of a flow chart.
Transformation of Energy – Energy can be converted from one form of energy to another form. Question 3.
Represent the various sources of energy with the help of a chart. Question 4.
Write a short note on the following –

1. Biomass energy
2. Hydroelectric plants
3. Atomic energy plant
4. Ocean energy
5. Geological energy
6. Magnetic potential energy

1. Biomass Energy –
Gobar and other bio-degradable wastes generate energy which is called biomass energy. ‘Ibis is obtained through bio gas plants. This is used as a house fuel and for lighting facility.

2. Hydroelectric Plants –
Big dams are built on rivers and then this collected water is dropped from a particular height on the turbines. Turbine is connected with the electric generator which gives electric
energy. This is known as hydro electric plants. Electric energy so generated is used in big cities and villages.

3. Atomic Energy Plants –
Atomic or Nuclear furnace can also generate electricity. This type of plant is known as Atomic energy plant. In Rawatbhata Chittorgarh district of Rajasthan has Atomic Energy plant from which electricity is being generated.

4. Ocean Energy –
Energy generated by. low tides, high tides, waves, etc. in an ocean is known as ocean energy.

5. Geological Energy –
The inner part of the earth has higher temperature. This heat energy or thermal energy can also he converted into electricity which is known as Geological geothermal energy.

6. Magnetic Potential Energy –
If there is any flowing charge or moving conductor in the magnetic field, then the capacity to do work which is generated due to the magnetic force on it, is known as magnetic potential energy. Question 5.
Separate the following examples according to potential and kinetic energy. Wind mill, Arrow-Bow, Sling-shot, Flowing water.