RBSE Class 8 Science Chapter 9: Work and Energy Solutions

Here, we have provided RBSE Class 8 Science Chapter 9 Work and Energy solutions. We have covered all the questions of the textbook, including the multiple-choice questions, fill-ups and matching exercises. Along with that, we are also offering several additional questions to help you prepare the best way possible.

The RBSE solutions for Class 8 provided by us are 100% accurate and detailed. Also, the additional questions here are based on the concepts covered in the textbook. You can rely on these solutions and practice these for your examinations.

Rajasthan Board Class 8 Science Chapter 9: BYJU’S Important Questions & Answers

RBSE Class 8 Science Chapter 9 Objective Questions: Textbook Important Questions and Solutions

Q1. The unit of energy is:

(A) Newton

(B) Kilogram

(C) Joule

(D) Watt

Answer: (C) Joule

Q2. The capacity of doing work is called:



(A) Power

(B) Force

(C) Momentum

(D) Energy

Answer: (D) Energy

Q3. One of the following is not fossil fuel:

(A) Petrol

(B) Wood

(C) Natural gas

(D) Diesel

Answer: (B) Wood

Q4. Which of the following apparatus is used to convert electric energy into sound? energy:

(A) Electric motors

(B) Electric magnet

(C) Electric heater

(D) Electric bell

Answer: (D) Electric Bell

RBSE Class 8 Science Chapter 9 Fill in the blanks: Textbook Important Questions and Solutions

Q5. The energy in objects due to its motion is called __________ of an object.

Answer: Kinetic Energy

Q6. Stressing the rubber in sling-shot, the __________ energy is stored in it

Answer: Potential

Q7. Electric cell used in a household converts __________ energy into electric energy.

Answer: Chemical

Q8. Unit of energy is __________.

Answer: Joule

RBSE Class 8 Science Chapter 9 Match Column A and Column B: Textbook Important Questions and Solutions

Q.

Energy Conversion Instrument
Electrical energy to sound energy Solar Cell
Electrical energy to heat energy Dynamo (generators)
Mechanical energy to electrical energy Electric Heater
Light energy to electrical energy Speaker

Answers:

Energy Conversion Instrument
Electrical energy to sound energy Speaker
Electrical energy to heat energy Electric Heater
Mechanical energy to electrical energy Dynamo (generators)
Light energy to electrical energy Solar Cell

RBSE Class 8 Science Chapter 9 Short Answer Type Questions: Textbook Important Questions and Solutions

Q1. Define work.

Answer: The action performed in order to produce a displacement by applying force on an object is called work.

Q2. What are the things on which work done on an object depends?

Answer: The work done on the object depends on the following:

(i) the displacement covered by an object.

(ii) the amount of force applied on the object, thus, Work = Force x Displacement.

Q3. Give the two names which store kinetic energy and potential energy in it on the basis of daily life observation.

Answer: Two examples which store kinetic energy and potential energy in it on the basis on daily life observation are as follows:

Water stored in the overhead tanks has potential and kinetic energy. A bird flying in the sky has both potential as well as kinetic energy.

Q4. How do we define heat energy conversion? Explain energy transfer on the basis of three different examples.

Answer: Heat energy can be defined as the energy that is stored in burning objects or hot objects. When this heat energy is converted into any other kind of energy, then it is called heat energy conversion.

Here are three examples of energy transfer:

a) Electric energy is converted into heat energy by an electric heater

b) Mechanical energy is converted into electrical energy by an electric generator

c) Light energy is converted into electrical energy by solar cells

RBSE Class 8 Science Chapter 9 Long Answer Type Questions: Textbook Important Questions and Solutions

Q5. What do you mean by global energy crisis? What are the measures you adopt to resolve the global energy crisis? Describe it in detail.

Answer:

Growth of population and increasing development in various fields and industries has led to increasing demand and use of conventional energy sources. These resources have limited storage of deposits. If such consumption of these resources continues, there will be a day when all the deposits of these resources will be completely depleted and exhausted. This will result in a global energy crisis.

To avoid this global energy crisis, it is necessary to use the resources wisely and meanwhile also try to search for alternate energy sources.

Here are the measures that we can take to resolve the global energy crisis:

– Solar energy should be used optimally

– Prefer to use biotic energy resources

– Turn off the automobiles while waiting at traffic signals

– Prevent the wastage of traditional energy sources

– When required, only then use electrical appliances

– In case there is no one in the room or an area, switch off the electrical appliances

– Pressure cookers, solar cookers, etc. can be used which will save energy

– Instead of using ordinary bulbs/tube lights, we can use LED bulbs/tube lights

– Build homes and buildings in such a way that they remain cool in summers and hot in winters. This will ensure less usage of ACs, electric heaters, etc.

Q6: Explain the differences between conventional energy sources and non-conventional energy sources with suitable examples.

Answer: The differences between conventional energy sources and non-conventional energy sources are as follows:

Conventional Energy Sources Non-conventional Energy Sources
1. The traditional sources of energy pollute the surroundings. 1. The non-traditional sources of energy are designed to be eco-friendly and hence produce no or very less pollution.
2. These have a lower decomposition rate than consumption rate. 2. These have a higher decomposition rate than consumption rate.
3. The conventional energy sources have limited reserves. 3. Non-conventional energy sources have unlimited reserves.
4. They should be used in a very controlled quantity. 4. They can be used in a larger quantity.
E.g. Coal, natural gas, diesel, petrol, etc. E.g. Sun, water, air, sea, earth, etc.

RBSE Class 8 Science Chapter 9 Additional Important Questions and Solutions

Q7. What do we mean by Geothermal energy?

Answer: Geothermal energy can be defined as the energy that is present in the depth of earth. With increasing depth, the temperature of the earth increases.

Electrical energy can be produced from this heat energy.

Q8. What do we mean by Fossil Fuel? Give examples.

Answer: Fossils are the remains of the plants and animals that were alive millions of years ago. Those plant and animal remains got mixed with the earth surface due to high pressure and temperature.

The fuel formed through the decomposition of such dead organisms through natural processes is called fossil fuel.

Examples of fossil fuels: gas, coal, petroleum, etc.

Q9. What do we mean by Potential energy? Cite examples.

Answer: Potential energy is the energy that a body holds in relation to other objects or due to change in its shape.

There are multiple examples where objects possess potential energy. Two of such examples can be:

i) A coiled spring possesses potential energy because of the change in its shape.

ii) Water that is behind a dam also contains potential energy in it.

Q10. How can we say that living and non-living bodies have the capacity to work?

Answer: Although we think that only living beings have capacity to do work, even non-living bodies have the capacity to do work. An ox pulling a cart is an example of a living being showing it has the capacity to do work.

We can run huge machines by the water falling on those machines from a suitable height, a generator can run by water steam using coal’s heat, etc. is an example of a non-living body exhibiting the capacity to do work. Hence, we can say that living and non-living bodies have capacity to do work.

Q11. What do we mean by bio-mass energy? Write its uses.

Answer: The waste products of animals like cows, dry leaves and wild plants are brewed or fermented in a digestive tank. During this process, a gas is produced which is called biogas, bio-mass or gobar gas. This gas produces smokeless fume. Thus, it is eco-friendly.

For generating biomass, often the energy sources are thought to be limited to plant wastes but that’s not the case. Even animal-derived materials are used for biomass generation. Biomass is the foundation of biofuels, immensely used in the production of electricity for heat production, as a substitute for fossil fuels.

Q12. What is Energy? What is the unit of energy? Explain the categorization of energy.

Answer: The ability to do work is called energy. The strength to do any kind of physical activity is what energy is.



There are two types of energy:

1. Kinetic energy (working)

2. Potential energy (static)

Kinetic Energy: The kinetic energy of an object is the energy that it possesses due to its motion.

Potential Energy:

As we know, an object can store energy as a result of its position. In the case of a bow and an arrow, when the bow is drawn, it stores some amount of energy, which is responsible for the kinetic energy it gains, when released.

Q13. How do we define work? What is its SI unit? Cite the expression for positive work done.

Answer: The action performed in order to produce a displacement by applying force on an object is called work.

The SI unit of work is Joule.

The expression for positive work done is:

Work = Force x displacement

Q14. How is kinetic energy different from potential energy?

Answer: Kinetic energy is the energy stored in an object due to its motion while potential energy is the energy stored in an object due to its position or state.

Also, velocity is a crucial factor when one calculates an object’s kinetic energy. However, velocity is nowhere related to an object’s potential energy.

Q15. What do we mean by Renewable energy?

Answer: Renewable energy is an energy that is obtained from natural phenomena and is continuously replenished. Sunlight, water, wind, tides, geothermal heat and biomass are a few examples of renewable energy. The energy that is offered by renewable energy resources is used in the following important areas:

– air cooling/heating

– water cooling/heating

– the rural sector

– electricity generation

– transportation.

As per a report by REN21 in 2016, the global consumption of energy by the use of renewable energy resources added to 19.2% in 2014 and 23.7% in 2015.

A lot of countries have begun to invest in these renewable energy resources because these resources will aid in establishing sustainable development.

Q16. Give 3 examples of objects having potential energy.

Answer: Given below are the examples of objects having potential energy:

Huge turbines can be rotated by the water falling from a suitable height is an example of potential energy stored in water due to its position (height).

The motion of stone shot by the sling-shot rubber is another example of potential energy stored in the object.

An arrow shot by a stiff string of a bow is also an instance of potential energy stored in the string due to change in the shape of the object.

Q17. Explain the working of key-based toy cars.

Answer: Spring is present inside the car. When we insert the key and rotate it, it presses the string. As a result, the car starts motion due to the change in position of the string present inside the toy car.

Q18. “An object works on another object”. Explain.

Answer: The first object loses its energy when it does work on the second object. The work done by the first object appears on the second object. As a result, the energy of the second object increases. Thus, we can say that an object works on another object.

Q19. What are the advantages and disadvantages of renewable energy?

Answer: Advantages of Renewable energy:

– There are various environmental and economic benefits of renewable energy.

– They do not produce any greenhouse gas.

– They reduce some types of air pollution.

– They can be produced using energy sources that would not deplete.

Disadvantages of Renewable energy:

It is cumbersome to produce the quantities of electricity that are as huge as the ones produced by fossil fuel generators.

Q20. What is displacement? Give an example.

Answer: The distance covered by any object in a certain direction is called its displacement.

An example of displacement would be: When a ball on the floor is pushed, then the ball travels some distance in a certain direction.

Q21. What will be the value of displacement if a person is walking around a circular path and he reaches back to the starting point? What will be the value of work done in such a case?

Answer: As displacement is the amount of distance between the initial and final position, here the displacement would be zero. This is because the initial and final position of the object are the same.

In such a case, work done is considered to be zero, because work = force x displacement. And the displacement is zero here. So, work done is zero too.

Q22. What do we mean by Ocean energy?

Answer: The energy that is obtained from high and low tides or strong waves in the ocean is called ocean energy.

Q23. What is light energy?

Answer: The energy that is stored in the sun, bulb, etc. is called light energy. Examples of light energy include heating the objects in sun rays, generation of electricity by solar cells.

Q24. What do we mean by Atomic energy?

Answer: Atomic energy is the energy obtained from nuclear fusion or fission. Electricity generation in the atomic (nuclear) reactor.

Q25. What do we mean by Magnetic energy?

Answer: Magnetic energy is the energy that is stored in a magnetic field. An example of magnetic energy would be the way iron objects are attracted towards a magnet.

Q26. What do we mean by Sound energy?

Answer: Sound energy is the energy that is stored in the sound or vibration of an object. An example of sound energy would be the sound obtained by the vibrations of various musical instruments.

Q27. What do we mean by Mechanical energy? Give examples.

Answer: Mechanical energy is the energy that is stored in an object due to its position or motion. Kinetic energy and potential energy are also forms of mechanical energy. Examples of mechanical energy due to motion would be objects and entities like water, air, vehicle, ball, car, etc. in motion.

Examples of mechanical energy due to the position or change in the shape of the object would be spring, sling-shot, arrow-bow, etc.

Q28. What do we mean by Chemical energy?

Answer: Chemical energy is the energy that is stored in the fuels. Chemical energy is converted into electrical energy in cells and batteries. The energy stored in all kinds of fuels is an example of chemical energy.

Q29. What are the conventional energy resources?

Answer: There are sources of energy that can not be reused. Such resources are called conventional sources of energy, also known as non-renewable energy resources.

Examples of such resources include coal, natural gas, petroleum, nuclear energy, etc.

It is assumed that lakhs of years ago, many plants and animals would have got buried in the earth’s surface. These remains got converted into mineral and petroleum. These are called fossil fuels. These are conventional energy resources.

Q30. Give examples of fossil fuels.

Answer: The examples of fossil fuels are:

– Natural gas

– Coal

– Petroleum

Q31. Give examples of mechanical energy.

Answer: Examples of mechanical energy due to motion would be objects and entities like water, air, vehicle, ball, car, etc. in motion.

Examples of mechanical energy due to the position or change in the shape of the object would be spring, sling-shot, arrow-bow, etc.

Q32. Give examples of heat energy.

Answer: Examples of heat energy would include running the engine through the heat energy of coal, motion set in vehicles due to the burning of petrol or diesel, etc.

Q33. Give examples of chemical energy.

Answer: Examples of objects or matter storing chemical energy are:

Petroleum, Coal, Natural gas, etc. All these convert chemical energy into light and heat energy during combustion.

Q34. Give examples of light energy.

Answer: Examples of light energy include the heating of objects in the presence of the sun, generation of electricity by solar cells, etc.

Q35. Give examples of electrical energy.

Answer: Examples of electrical energy are lightening of a bulb, working of an electric fan, electric motors, etc.

Q36. Give examples of magnetic energy.

Answer: Examples of magnetic energy include:

– iron objects being attracted towards a magnet

– magnets in the fridge to seal the doors when closed

– magnets on the fridge cling to the surface of the fridge due to the magnetic field.

Q37. Give examples of sound energy.

Answer: Examples of sound energy are:

– the sound produced by aeroplanes while taking off

– the sound of a balloon popping off

– the sound produced by various musical instruments

Q38. Give examples of atomic energy.

Answer: Examples of atomic energy include

– atomic bombs

– nuclear power stations

– electricity generation in atomic reactors

– nuclear submarines

Q39. What are the sources of chemical energy, sound energy, magnetic energy and atomic energy?

Answer: Source of chemical energy: fuels

Source of sound energy: sound or vibration of objects

Source of magnetic energy: magnetic field

Source of atomic energy: nuclear fusion or fission

Q40. How many forms of energy sources are there? Cite examples.

Answer: There are two forms of energy sources:

1. Renewable source of energy

2. Non-renewable source of energy

Based on their sources, the following are examples of types of energy:

1. Renewable source:

-Solar energy

-Wind energy

-Geothermal energy

2. Non-renewable source:

-Natural gas

-Coal

-Petroleum products

Q41. What are the sources and examples of Renewable Energy?

Answer: Renewable energy is that energy that will never get depleted. It is renewed. Renewable energy is very crucial. It is very different from the energy that is obtained from fossil fuels like oil, natural gas or coal.

Here are some examples of renewable energy sources:

– Wind energy

– Geothermal energy

– Solar energy

– Biomass energy

– Hydropower

These sources will exist for a longer period of time and can easily be replenished and renewed often. Biomass, nuclear, geothermal, wind, sun, tides, and waves are all examples of sustainable sources of energy.

Q42. Explain any 4 types of Renewable energy?

Answer: Types of Renewable Energy


Solar Energy:
With the help of solar collectors, the heat and light energy from the sun is exploited. Photovoltaics, (CSP) concentrated solar power, concentrator photovoltaics, artificial photosynthesis, solar heating, and solar architecture are various types of solar collectors. This collected solar energy is then utilized in order to provide heat, light, and various other forms of electricity.

Wind Energy: Wind energy is the energy we obtain from winds. For obtaining wind energy, windmills have been adopted for many years in order to pump out water from the ground. Large and tall wind turbines are used that allow winds to produce electricity.

Geothermal Energy: It is the energy that is generated from the thermal energy which is stored in the earth. The heat energy is captured on sources such as hot springs and volcanoes and this heat is directly used by industries for heating the water and other purposes.

BioEnergy: The waste products of animals like cows, dry leaves and wild plants are brewed or fermented in a digestive tank. During this process, a gas is produced which is called biogas, bio-mass or gobar gas. This gas produces smokeless fume. Thus, it is eco-friendly.

For generating biomass, often the energy sources are thought to be limited to plant wastes but that’s not the case. Even animal-derived materials are used for biomass generation. Biomass is the foundation of biofuels, immensely used in the production of electricity for heat production, as a substitute for fossil fuels.

Q43. What do we mean by Hydroelectricity?

Answer: Hydroelectricity energy is another alternative source of energy that is generated by the construction of dams and reservoirs on the flowing water, the kinetic energy from the flowing water is used to run the turbines which generate electricity. According to statistics, hydroelectricity generated around 16.6% of the global energy resources and constituted about 70% of all the renewable electricity.

A tidal power which converts the energy of tides and Wave power which captures the energy from the surface of the ocean waves for power generation. These two forms of hydropower also have huge potential in electric power generation.

Q44. What do we mean by Non-renewable energy?

Answer: In nature, energy sustains in its free form. Some of this energy is available to an infinite extent as it is replenishable. Such energy is called renewable energy. But some energy sources are limited in nature. Such energy is called non-renewable. The non-renewable energy does not get renewed at a required rate for maintaining its sustainable extraction.

The energy from fossil fuels such as coal, crude oil, natural gas and uranium are examples of non-renewable energy. As a contrast to renewable energy, non-renewable energy requires human involvement to make it appropriate for consumption. Carbon is the main ingredient of Fossil fuels.

Q45. Explain the types of non-renewable energy resources?

Answer: Non-renewable energy mostly comprises fossil fuels. Along with fossil fuels, nuclear fuels are also non-renewable.

Fossil Fuels

Fossils are the remains of the plants and animals that were alive millions of years ago. Those plant and animal remains got mixed with the earth surface due to high pressure and temperature.

The fuel formed through the decomposition of such dead organisms through natural processes is called fossil fuel.

Examples of fossil fuels: gas, coal, petroleum, etc.

Nuclear fuels

Nuclear fuel is the ingredient or the fuel used in the nuclear power stations in order to generate heat to run turbines. When this nuclear fuel goes through nuclear fission, heat is produced.

Solutions for all the questions in the RBSE textbook have been answered here. These solutions have been crafted by our subject-matter experts meticulously keeping in mind the standards set forth by the board. Prepare yourself the best way for your examinations and understanding of the concepts through solving all the above-mentioned questions. Stay tuned to get all the information you will require for excelling in your studies.

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