Energy (VIVA EDUCATION)
EXERCISES
BE PROMPT
A. Fill in the blanks.
1. The SI unit of energy is Joule.
2. The energy stored in nucleus of an atom is called Nuclear Energy.
3. Light energy is utilised by the plants during the process of photosynthesis.
4. In an electric bulb, the electrical energy gets converted into light and heat energy.
5. In a microphone, the sound energy gets converted into the electrical energy.
B. State whether the following statements are true (T) or false (F). Correct the false statements.
1. A book lying on the study table has no energy. [F]
= A book lying on the study table has potential energy.
2. The energy cannot be transformed from one form to another form. [F]
= The energy can be transformed from one form to another form.
3. A solar cell converts the light energy to electrical energy. [T]
4. Greater the mass of the body, lower is the kinetic energy of the body. [F]
= Greater the mass of the body, more is the kinetic energy.
5. The muscular energy is derived from the chemical energy stored in the food that we eat. [T]
C. Choose the correct option.
1. The potential energy is directly proportional to ____________ .
(a) mass and height of the body. [ ]
(b) mass of the body. [✓]
(c) height of the body. [ ]
(d) none of these. [ ]
2. While burning the wood, the chemical energy changes to ___________ .
(a) kinetic energy. [ ]
(b) heat energy. [✓]
(c) potential energy. [ ]
(d) mechanical energy. [ ]
3. When you kick a ball lying in the ground, the potential energy changes to __________ .
(a) heat energy. [ ]
(b) electrical energy. [ ]
(c) kinetic energy. [✓]
(d) nuclear energy. [ ]
4. Which of the following is not a unit of energy?
(a) Joule. [ ]
(b) N m. [ ]
(c) Newton. [✓]
(d) Calorie. [ ]
5. When fire crackers burst, the chemical energy changes to _________ .
(a) heat energy. [ ]
(b) sound energy. [ ]
(c) light energy. [ ]
(d) heat, sound and light energy. [✓]
D. Match the columns.
=
|
A |
B |
|---|---|
|
1. Heat energy. |
(a) Running water. [5] |
|
2. Nuclear energy |
(b) MRI. [4] |
|
3. Solar energy |
(c) Burning of coal. [1] |
|
4. Magnetic energy |
(d) Atom bomb. [2] |
|
5. Kinetic energy |
(e) Sun. [3] |
SHORT AND PRECISE
A. Show the following processes in the form of flowcharts.
1. Energy in action and stored energy.
=
2. Transformation of energy in a hydroelectric power plant.
=
B. Give reasons for the following statements.
1. When a piece of rock stone falls on the ground form a height, it makes deeper impression.
= Because it possesses more potential energy due to its still position before falling.
2. Light energy helps in the sustenance of life on the earth.
= The light from the sun helps green plants to prepare food through the process of photosynthesis. The food is then consumed by other living organisms in various forms like fruits, vegetables and seeds. Also, the oxygen released during photosynthesis is essential for respiration of organisms. Hence, light energy sustains life on earth.
3. In a roller coaster, the potential and kinetic energy keeps on changing.
= When the roller coaster is at the top, it has the maximum potential energy and the kinetic energy is zero. On the other hand, when the roller coaster is at the bottom, it has the maximum kinetic energy and the potential energy is zero.
4. Water stored in dams is able to turn the blades of turbine.
= Huge amount of water is stored in dams, which are built at a height. Water at such height possesses potential energy. That is why is able to turn the blades of turbine.
5. The motion of a simple pendulum is an example of law of conservation of energy.
= In a pendulum, the energy gets transformed from kinetic energy to potential energy and vice versa. Therefore, there is a continuous transformation of energy taking place in a pendulum as it continues to oscillate. Its total mechanical energy is equal to the sum of potential and kinetic energies remain conserved.
C. Answer in short.
1. What is the gravitational potential energy?
= Gravitational potential energy is the energy gained by a body when it is raised to some height with respect to ground.
2. Why do we get hurt when we come in front of moving bicycle?
= Moving bicycle has kinetic energy. Kinetic energy of a body is directly proportional to the square of the speed of the body. This means a fast moving object will have more kinetic energy. That is why we get hurt when we come in front of moving bicycle.
3. What happens when a rubber band is stretched?
= The energy spent in stretching the band gets stored in the rubber band in the form of potential energy. When the band is released, it flies in the air before regaining its original shape.
4. Name five different forms of energy.
= Five different forms of energy are - Heat energy, Light energy, Sound energy, Electrical energy and Muscular energy.
AT LENGTH
A. Explain the following terms.
1. Energy.
= The ability of a body to do work.
2. Magnetic energy.
= The energy stored in a magnet due to which it exerts force on iron objects and other magnets.
3. Sound energy.
= A form of energy produced by vibrating bodies.
4. Work.
= Displacement of a body due to the application of force.
5. Chemical energy.
= The energy that is stored in molecular bonds, the forces that hold molecules together.
B. Differentiate between the following.
1. Kinetic energy and potential energy.
=
|
Kinetic Energy |
Potential Energy |
|---|---|
|
1. It is the energy possess by a body due to its motion. |
1. It is the energy possess by a body due to its
position or change in shape. |
|
2. It depends on the mass and speed of the body. |
2. It depends on the mass and height of the body
above the ground. |
|
3. It has no further division. |
3. It is further divided into two categories –
Gravitational potential energy and Elastic potential energy. |
2. Light energy and heat energy.
=
|
Light Energy |
Heat Energy |
|---|---|
|
1. Heat energy
is a form of energy which is responsible for the sensation of hotness or coldness. |
1. Light energy is also a form of energy which makes
things visible to us. |
3. Chemical energy and nuclear energy.
=
|
Chemical Energy |
Nuclear Energy |
|---|---|
|
1. The energy that is stored in molecular bonds is
called chemical energy. |
1. The energy stored in the nucleus of an atom is
known as nuclear energy. |
|
2. It produce lesser energy is used in processes
like transportation and cooking. |
2. It produce huge amount of energy like nuclear
electricity. |
C. Read the given paragraph on energy transformation in the parts of an automobile engine. Identify the incorrect parts of the process.
Firstly, the chemical energy of the fuel gets converted to kinetic energy. This heat, in turn, move the piston of the engine, thereby converting heat energy to nuclear energy. The movement of piston cause the automobiles to move, hence, converting mechanical energy to potential energy. Some of the kinetic energy then gets stored in the form of light energy in the battery. Also some of the potential energy converted into light energy by the headlights and some into mechanical energy by the horn.
= Firstly, the chemical energy of the fuel gets converted to heat energy. This heat, in turn, move the piston of the engine, thereby converting heat energy to mechanical energy. The movement of piston cause the automobiles to move, hence, converting mechanical energy to kinetic energy. Some of the kinetic energy then gets stored in the form of light energy in the battery. Also some of the kinetic energy converted into light energy by the headlights and some into sound energy by the horn.
D. Answer in detail.
1. Can a body at rest posses energy? Explain your answer with an example.
= Yes, a body at rest posses energy. The energy possesses by a body due to its position or change in shape.
For example, water is stored in dams or reservoirs at a height. This water possesses potential energy and hence when it falls from above it is capable of doing work like turning blades of a turbine.
2. What are the two factors on which the kinetic energy depends? Explain.
= The kinetic energy depends on the following two factors :-
i. The mass of the body.
The kinetic energy of a body is directly proportional to its mass. The heavier an object, the more its kinetic energy.
ii. The speed of the body.
The kinetic energy of a body is also directly proportional to the square of the speed of the body. This means a fast moving object will have more kinetic energy.
3. Explain energy transformation in a hydroelectric power plant.
= In a hydroelectric power plant, huge amount of water is stored in the dams which are built at a height. Water at such height possesses potential energy. When water from a height is released, its stored potential energy gets converted into kinetic energy. The kinetic energy of the moving water is then used to move the blades of a turbine which then helps in producing electricity.
4. What is the law of conservation of energy? Explain with an example.
= The law of conservation of energy states that energy can neither be created nor destroyed, but it converted form one form to another. The other way to state the law is 'the total energy of a system is always conserved'.
For example, in a roller coaster, when the roller coaster car is at the top of the coaster, it has the maximum potential energy. As it starts coming down, its height starts decreasing and hence it potential energy decreases and kinetic energy increases The the bottom-most point of the ride, its potential energy becomes zero (as height = 0) and kinetic energy becomes maximum. The process goes on. The potential and kinetic energies keep on interchanging. In the entire path, the total mechanical energy (sum of potential energy and kinetic energy) remains conserved. However, some energy gets wasted due to friction.
5. Two rocks A and B of masses 100 kg and 20 kg respectively are setting at an edge of a cliff. Which rock has a higher potential energy? When the rocks are made to fall on the ground, which rock make a deeper impression on the ground? Give reason.
= Rock A has a higher potential energy.
Rock A will make a deeper impression on the ground.
Potential energy of a body directly proportional to its mass. Greater the mass of an object, more is its potential energy. Here rock A has much more mass than rock B. So rock A has greater potential energy than rock B. It will make deeper impression.
6. What is mechanical energy? What are its two types? Give examples.
= Mechanical energy is the energy possessed by a body due to its position or motion.
The two types of mechanical energy are - Kinetic energy and Potential energy.
Example of kinetic energy is a moving ball, flowing water, a flying bird, etc.
Example of potential energy is stored water in the dam.
Review Your Learning
A. Answer in one word.
1. The ability to do work.
= Energy.
2. The energy of the object due to its position.
= Potential energy.
3. The prime energy needed for sustaining life on the earth.
= Light energy.
4. The energy released form nuclei of atoms.
= Nuclear energy.
5. The energy derived from the food that we eat.
= Muscular energy.
B. State whether the given statements are true (T) or false (F).
1. When put in use the potential energy can be changed into kinetic energy. [T]
2. The energy of flowing water is converted into electrical energy using dams. [T]
3. There is always a loss of energy and total energy is not conserved. [F]
4. In a generator, the mechanical energy is converted into electrical energy. [T]
5. Electrical energy is converted into sound energy in door bell. [T]
C. Match the columns.
=
|
Column
A |
Column
B |
|---|---|
|
1. Photosynthesis |
(a) Electrical energy to
mechanical energy. [2] |
|
2. Washing machine. |
(b) Electrical energy to heat
energy. [3] |
|
3. Heater. |
(c) Chemical energy to heat and
mechanical energy. [5] |
|
4. Burning of coal. |
(d) Chemical energy to heat
energy. [4] |
|
5. Car engine. |
(e) Light energy to chemical
energy. [1] |
D. Explain in following terms.
1. Heat energy.
= A form of energy which is responsible for the sensation of hotness and coldness.
2. Magnetic energy.
= The energy stored in a magnet due to which it exerts force on iron objects and other magnets.
3. Elastic potential energy.
= The energy stored in a body when work is done to deform, stretch or compress it.
4. Electrical energy.
= The energy produced by the flow of electric charge (electrons) through a conductor.
5. Atom.
= Atoms are the tiny particles that make up every object in the universe.
E. Answer the following questions.
1. State the energy transformations that take place in a power plant.
=In a thermal power plant, the chemical energy of fuels like coal is converted into heat energy. This heat is used to boil water, thus the heat energy gets converted into kinetic energy in the form of steam. The steam moves the shaft of a turbine and gets transformed into mechanical energy, which in turn produces electrical energy with the help of a generator.
2. Explain how the mechanical energy is conserved in a roller coaster ride.
= In a roller coaster, when the roller coaster car is at the top of the coaster, it has the maximum potential energy. As it starts coming down, its height starts decreasing and hence it potential energy decreases and kinetic energy increases The the bottom-most point of the ride, its potential energy becomes zero (as height = 0) and kinetic energy becomes maximum. The process goes on. The potential and kinetic energies keep on interchanging. In the entire path, the total mechanical energy (sum of potential energy and kinetic energy) remains conserved. However, some energy gets wasted due to friction.
3. What are the different energy transformations that take place in different parts of an automobile engine?
= The parts of an engine of an automobile help convert energy from one form to another.
Firstly, the chemical energy of the fuel gets converted to heat energy. This heat in turn moves the piston of the engine thereby converting heat energy to mechanical energy. The movement of the piston causes the automobile to move, hence converting mechanical energy to kinetic energy. This kinetic energy is converted into different forms to do various works. It gets stored as chemical energy in the battery which gets converted into light energy by the headlights, and sound energy by the horn. Some kinetic energy is lost in overcoming friction between tyres and road, and between other parts of the vehicle.
4. Explain five different forms of energy with examples.
= Five different forms of energy are -
i. Heat Energy :- Heat energy is a form of energy which is responsible for the sensation of hotness or coldness. We get heat energy primarily from the sun. Besides, we also get heat energy by burning fuels like wood, coal and petrol. This energy is useful in activities like cooking, generating electricity and running steam engines. Heat energy is also called thermal energy.
ii. Electrical Energy :- The energy produced by the flow of electric charges (electrons) through a conductor is known as electrical energy. When electrical energy is made available for use through the wires or cables, we call it electricity. The electricity that we get at our homes is used to run electrical appliances like bulb, fans, television, computer and washing machine.
iii. Muscular Force :- The energy stored in the muscles of our body is called muscular energy. We obtain this energy from food we eat. When food is broken down into smaller particles, chemical energy is released which is stored in our muscles. This muscular energy is then utilised for various activities we perform.
iv. Magnetic Energy :- We already know that magnets exert force on iron objects and other magnets. The energy stored in a magnet due to which it exerts force on iron objects and other magnets is known as magnetic energy. This form of energy is used for various purposes such as lifting heavy iron objects, magnetic separation of iron objects and medical purposes.
v. Nuclear Energy :- The energy stored in the nucleus of an atom is known as nuclear energy. Atoms are the tiny particles that make up every object in the universe. There is enormous energy in the bonds that holds atoms together. When the nucleus of an atom splits or two different nuclei combine together, a large amount of energy is released in the form of heat. This enormous energy can be utilised for generation of electricity.
5. Can energy be destroyed? Explain.
= Energy can not be destroyed. According to the law of conservation of energy, energy can neither be created nor destroyed, but it gets converted form one form to another.
The total energy of the system remains conserved means that if some energy gets transformed into different forms of energy, the total sum of all the energy remains same as before.