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Class V Science T1U3 Energy Textbook Solutions
3.ENERGY
I. Choose the correct answer.
1. 1. When diesel is burnt chemical energy is converted into ________
a) wind energy b) heat energy c) solar energy d) sound energy
Ans:b) heat energy
2. Running water possesses ______
a) potential energy b) chemical energy c) kinetic energy d) sound energy
Ans:c) kinetic energy
3. Unit of energy is ________
a) kilogram b) newtonc) kelvin d) joule
Ans:d) joule
4. Which one of the following requires wind energy?
a) Bicycle b) Photosynthesis c) Parachute d) Automobiles
Ans:c) Parachute
5. Cow dung possesses ______
a) kinetic energy b) chemical energy c) solar energy d) heat energy
Ans:b) chemical energy
II. Find out the energy conversion that takes place in the following.
1. Iron box : Chemical energy Heat energy
2. Electric Iron box : _______________ _______________
Ans: Electrical energy → Heat energy
3. Electric fan : _______________ _______________
Ans: Electrical energy → Kinetic energy
4. Speaker : _______________ _______________
Ans: Electrical energy → Sound energy
5. Generator : _______________ _______________
Ans: Kinetic energy → Electrical energy
III. Find out the form of energy possessed by the following things.
1. A rock on the top of a hill - Potential energy
2. A rolling ball - Kinetic energy
3. Charcoal - Chemical energy
4. Water falls - Kinetic energy
5. Battery - Chemical energy
IV. Match the following.
V. Say True or False.
1. An apple falling from a tree is an example for kinetic energy.
Ans:True
2. Electrical energy is used to run electric trains.
Ans:True
3. Heat energy cannot be produced by friction.
Ans:False.
Heat energy can be produced by friction.
4. Potential energy and heat energy are the two forms of mechanical energy.
Ans:False
Potential energy and Kinetic energy are the two forms of mechanical energy.
5. The unit of energy is joule.
Ans:True
VI. Answer in brief.
1. What is energy?
Ans:Energy is defined as the capacity to do work.
2. What are the different forms of energy?
Ans:Mechanical energy, heat energy, light energy and wind energy are some of the different forms of energy.
3. What are the uses of mechanical energy?
Ans:
Mechanical energy can be used to do many works.
In hydro electric plants, kinetic energy of water is converted into electrical energy.
Wind mills convert kinetic energy of winds into electrical energy.
4. State the law of conservation of energy.
Ans:
Energy cannot be created and it cannot be destroyed also. It is changed from one form to another form or transferred from one object to another object.
5. Mention the uses of light energy.
Ans:
We are able to see objects with the help of light energy.
Plants use light energy to synthesize their food.
VII. Answer in detail.
1. Explain the types of mechanical energy.
Ans:
Energy possessed by an object due to its position is called mechanical energy. Mechanical energy can be classified into two.
Kinetic energy
Potential energy
Kinetic energy
Energy possessed by a moving object is known as kinetic energy. It is also known as energy of motion.
Examples: Moving car, Cricket ball bowled by a player, Bullet coming out of a gun.
Potential energy
Energy possessed by an object which is at rest is known as potential energy. It is also known as stored energy of position.
Examples: Object lifted above, Stone in the stretched rubber, Water in the dam.
2. Explain conservation of energy.
Ans:
Energy cannot be created and it cannot be destroyed also.
It is changed from one form to another form or transferred from one object to another object.
Example:
1. Potential energy → Kinetic energy → Electric energy
Water stored in water dams possesses potential energy →
When water falls down, potential energy of water is converted into kinetic energy →
Kinetic energy of water rotates the turbines and electric energy is generated.
2. Electrical energy → Heat energy
Current flows into the devices-Electrical energy
