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# Selina solutions for Class 7 Physics chapter 3 - Energy

#### Selina Selina Concise Physics - Middle School Class 7 ## Chapter 3: Energy

#### Selina solutions for Class 7 Physics Chapter 3 [Page 0]

Write true or false

A man going up has potential energy and kinetic energy both.

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A gum bottle lying on a table has no energy.

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In an electric fan, electrical energy changes into the mechanical energy.

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Potential energy changes into kinetic energy when it is put to use

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One form of energy cannot be converted into another form.

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There is always some loss of energy in conversion from one form of energy to another form, so the total energy is not conserved.

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The energy of flowing water can be converted into electric energy (electricity).

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An electric fan converts electrical energy into .................... energy.

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Cooking gas converts .............energy into heat energy.

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Energy possessed by a compressed spring is ............. energy.

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The ability to do work is called ...........

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The energy possessed by a body due to its position is called .................energy.

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The energy possessed by a body due to its motion is called ............energy.

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Green plants convert ...........energy into chemical energy.

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The S.I.unit of energy is ............

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An object falling freely from the roof of a multistorey building has ...................... and ...................energy when halfway down the building.

Match the following columns

 COLUMN A COLUMN B 1. Running water 1. heat energy 2. Burning 2. vibrations 3.Energy 3.atom bomb 4.Sound energy 4.kinetic energy 5.Nuclear energy 5.joule

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When we rub our hands

1.  kinetic energy changes into potential energy
2.  mechanical energy changes into heat energy
3.  potential energy changes into kinetic energy
4.  heat energy changes into mechanical energy.

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A ball rolling on the ground possesses

1.  kinetic energy
2.  potential energy
3.  no energy
4.  heat energy

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The energy stored in an electric cell is

1.  chemical energy
2.  electrical energy
3.  heat energy
4.  mechanical energy

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When a bulb lights up on passing current, the change of energy is

1.  from electrical energy to heat energy
2.  from electrical energy to light energy
3.  from electrical energy to heat and light energy
4.  from electrical energy to mechanical energy.

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The correct statement is

1.  Both work and energy have the same units
2.  Potential energy of a body is due to its motion
3.  Kinetic energy of a body is due to its position or state

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According to law of conservation of energy, energy changes from one form to another form, but the total energy of that system

1.  increases
2.  decreases
3.  alternates
4.  remains the same

#### Selina solutions for Class 7 Physics Chapter 3 [Page 0]

Define the term energy.

State the unit of energy and define it.

Name five different forms of energy.

What are the two kinds of mechanical energy.

What is potential energy ? State its unit.

Give one example of a body that has potential energy,  due to its position .

Give one example of a body that has potential energy, in due to its state.

State two factors on which the potential energy of a body at a certain height above the ground depends.

Two bodies A and B of masses 10 kg and 20 kg respectively are at the same height above the ground. Which of the two has the greater potential energy ?

A bucket full of water .is on the first floor of your house and another identical bucket with same quantity of water is kept on the second floor. Which of the two has greater potential energy ?

Define the term kinetic energy. Give one example of a body which possesses kinetic energy.

State two factors on which the kinetic energy of a moving body depends.

Two toy-cars A and B of masses 500 g and 200 g respectively are moving with the same speed. Which of the two has the greater kinetic energy?

A cyclist doubles his speed. How will his kinetic energy change: increase, decrease or remain same ?

Name the form of energy which a wound up watch spring possess.

Can a body possess energy even when it is not in motion ? Explain your answer with an example.

Name the type of energy (kinetic or potential) possessed by the following :
A moving cricket ball.

Name the type of energy (kinetic or potential) possessed by the following :

A stone at rest on the top of a building.

Name the type of energy (kinetic or potential) possessed by the following :

A compressed spring.

Name the type of energy (kinetic or potential) possessed by the following :

A moving bus.

Name the type of energy (kinetic or potential) possessed by the following :

A bullet fired from a gun.

Name the type of energy (kinetic or potential) possessed by the following :
Water flowing in a river.

Name the type of energy (kinetic or potential) possessed by the following :

A stretched rubber band.

Give one example to show the conversion of potential energy to kinetic energy when put in use.

State the energy changes that occur in the following :

The unwinding of a watch spring.

State the energy changes that occur in the following :

Burning coal while operating a steam engine.

State the energy changes that occur in the following :

Lighting of a torch bulb.

State the energy changes that occur in the following :

An electric generator (or dynamo).

Energy can exist in several forms and may change from one form to another. Give two examples to show the conversion of energy from one form to another.

Give one relevant example for each of the following transformation of energy :

Electrical energy to heat energy.

Give one relevant example for each of the following transformation of energy :

Electrical energy to mechanical energy.

Give one relevant example for each of the following transformation of energy :

Electrical energy to light energy.

Give one relevant example for each of the following transformation of energy :

Chemical energy to heat energy.

Give one relevant example for each of the following transformation of energy :

Chemical energy to light energy.

What do you mean by conservation of mechanical energy? State the condition when does it hold.

Give one example to show that the sum of potential energy and kinetic energy remains constant if friction is ignored.

A ball is made to fall freely from a height. State the kind/ kinds of energy possessed by the ball when it is at the highest point .

A ball is made to fall freely from a height. State the kind/ kinds of energy possessed by the ball when it is just in the middle .

A ball is made to fall freely from a height. State the kind/ kinds of energy possessed by the ball when it is at the ground.

State the changes in form of energy while producing hydro electricity.

## Chapter 3: Energy

#### Selina Selina Concise Physics - Middle School Class 7 ## Selina solutions for Class 7 Physics chapter 3 - Energy

Selina solutions for Class 7 Physics chapter 3 (Energy) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Selina Concise Physics - Middle School for Class 7 solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com provide such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 7 Physics chapter 3 Energy are Energy as Capacity to Do Work, Units of Energy (Joule and Calorie), Different Forms of Energy, Inter-conversion of Energy, Concept of Law of Conservation of Energy, Law of Conservation of Energy: Real World Examples.

Using Selina Class 7 solutions Energy exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 7 prefer Selina Textbook Solutions to score more in exam.

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