Selina solutions for Concise Physics Class 8 ICSE chapter 4 - Energy [Latest edition]

Chapter 4: Energy

Objective questions [Pages 76 - 77]

Selina solutions for Concise Physics Class 8 ICSE Chapter 4 Energy Objective questions [Pages 76 - 77]

Objective questions | Q 1.1 | Page 76

A coolie does no work against the force of gravity while carrying a luggage on a road.

• True

• False

Objective questions | Q 1.2 | Page 76

The energy stored in water of a dam is the kinetic energy.

• True

• False

Objective questions | Q 1.3 | Page 76

The energy of a flying kite is kinetic energy.

• True

• False

Objective questions | Q 1.4 | Page 76

Work done by a boy depends on the time in which he does work.

• True

• False

Objective questions | Q 1.5 | Page 76

Power spent by a body depends on the time for which it does work.

• True

• False

Objective questions | Q 2.01 | Page 76

Work is said to be done by a forte only when ................

Objective questions | Q 2.02 | Page 76

Work done = Force × ........................................

Objective questions | Q 2.03 | Page 76

The energy of a body is its capacity to do .........

Objective questions | Q 2.04 | Page 76

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

Objective questions | Q 2.05 | Page 76

The potential energy of a body is due to its state of ................... and kinetic energy of body is due to its ...............

Objective questions | Q 2.06 | Page 76

Gravitational potential energy U = mass × force of gravity on unit mass × ..........

Objective questions | Q 2.07 | Page 76

Kinetic energy = 1/2 × mass × ............

Objective questions | Q 2.08 | Page 76

Power P= ............ /time taken.

Objective questions | Q 2.09 | Page 76

The S.I. unit of power is ..........

Objective questions | Q 2.1 | Page 76

1 H.P. = .........

Objective questions | Q 3 | Page 77

Match the following

 column A Column B A stone at a height power A Moving ball joule Energy work done in 1 s Power potential energy Watt kinetic energy
Objective questions | Q 4.1 | Page 77

The S.I. unit of work is

• second

• metre

• joule

• newton

Objective questions | Q 4.2 | Page 77

No work is done by a force if the body

• moves in direction of force

• does not move

• moves in opposite direction

• none of the these

Objective questions | Q 4.3 | Page 77

Two coolies A and B do some work in time 1 minute and 2 minute respectively. The power spent is

• same by both coolies

• is more by coolie A than by B

• is less by coolie A than by B

• nothing can be said.

Objective questions | Q 4.4 | Page 77

The expression of power P is

• P = mgh

• P = P = 1/2 Mv2v

• P = F × d

• P = F × d/t

Objective questions | Q 4.5 | Page 77

1 H.P. is equal to

• 1 W

• 1 J

• 746 J

• 746 W

Objective questions | Q 4.6 | Page 77

When a boy doubles his speed, his kinetic energy becomes

• half

• double

• four times

• no change

Objective questions | Q 4.7 | Page 77

A boy lifts a luggage from height 2 m to 4 m. The potential energy will become

• half

• double

• one-third

• one-fourth

Short/Long Answer questions [Pages 77 - 78]

Selina solutions for Concise Physics Class 8 ICSE Chapter 4 Energy Short/Long Answer questions [Pages 77 - 78]

Short/Long Answer questions | Q 1 | Page 77

Define work.

Short/Long Answer questions | Q 2 | Page 77

When does a force perform work?

Short/Long Answer questions | Q 3 | Page 77

State two conditions when no work is done by a force.

Short/Long Answer questions | Q 4 | Page 77

In which of the following cases is work being done :
(a) A boy pushing a rock
(b) A boy climbing up the stairs
(c) A coolie standing with a box in his head
(d) A girl moving on the road.

Short/Long Answer questions | Q 5 | Page 77

A coolie is moving on a road with a luggage on his head. Does he perform work against the force of gravity? Give reason for your answer.

Short/Long Answer questions | Q 6 | Page 77

The moon is revolving around the earth in a circular path. How much work is done by the moon?

Short/Long Answer questions | Q 7 | Page 77

Write the expression for work done by a force.

Short/Long Answer questions | Q 8 | Page 77

State the S.I. unit of work and define it.

Short/Long Answer questions | Q 9 | Page 77

State two factors on which the work done on a body depends.

Short/Long Answer questions | Q 10 | Page 77

Define the term energy.

Short/Long Answer questions | Q 11 | Page 77

State the S.I. unit of energy.

Short/Long Answer questions | Q 12 | Page 77

Define 1 joule of energy.

Short/Long Answer questions | Q 13 | Page 77

How is work related to energy?

Short/Long Answer questions | Q 14 | Page 77

What are the two kinds of mechanical energy?

Short/Long Answer questions | Q 15 | Page 77

What is potential energy? State its unit.

Short/Long Answer questions | Q 16 | Page 77

Give one example of a body that has potential energy, in each of the following:
(i) due to its position,
(ii) due to its state.

Short/Long Answer questions | Q 17 | Page 78

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

Short/Long Answer questions | Q 18 | Page 78

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 greater potential energy?

Short/Long Answer questions | Q 19 | Page 78

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

Short/Long Answer questions | Q 20 | Page 78

Write the expression for the gravitational potential energy explaining the meaning of the symbols used.

Short/Long Answer questions | Q 21.1 | Page 78

A body of mass m is moved from ground to a height h. If the force of gravity on mass of 1 kg is g newton, find the force needed to lift the body.

Short/Long Answer questions | Q 21.2 | Page 78

A body of mass m is moved from ground to a height h. If force of gravity on mass of 1 kg is g newton, find the work done in lifting the body.

Short/Long Answer questions | Q 21.3 | Page 78

A body of mass m is moved from ground to a height h. If force of gravity on mass of 1 kg is g newton, find the potential energy stored in the body.

Short/Long Answer questions | Q 22 | Page 78

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

Short/Long Answer questions | Q 23 | Page 78

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

Short/Long Answer questions | Q 24 | Page 78

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

Short/Long Answer questions | Q 25 | Page 78

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

Short/Long Answer questions | Q 26 | Page 78

Write the expression for the kinetic energy of a body explaining the meaning of the symbols used.

Short/Long Answer questions | Q 27 | Page 78

A ball of mass M is moving with a speed v. What is its kinetic energy?

Short/Long Answer questions | Q 28 | Page 78

Name the form of energy stored in a wound up spring of a watch.

Short/Long Answer questions | Q 29 | Page 78

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

Short/Long Answer questions | Q 30.1 | Page 78

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

Short/Long Answer questions | Q 30.2 | Page 78

Name the type of energy (kinetic or potential) possessed by the following A stone at rest on the top of a building.

Short/Long Answer questions | Q 30.3 | Page 78

Name the type of energy (kinetic or potential) possessed by the following A compressed spring.

Short/Long Answer questions | Q 30.4 | Page 78

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

Short/Long Answer questions | Q 30.5 | Page 78

Name the type of energy (kinetic or potential) possessed by the following A bullet fired from a gun.

Short/Long Answer questions | Q 30.6 | Page 78

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

Short/Long Answer questions | Q 30.7 | Page 78

Name the type of energy (kinetic or potential) possessed by the following  A stretched rubber band.

Short/Long Answer questions | Q 31 | Page 78

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

Short/Long Answer questions | Q 32 | Page 78

State the energy changes that occur in a watch spring while it unwinds.

Short/Long Answer questions | Q 33.1 | Page 78

Give reasons for the following. No work is done if a man is pushing against a wall.

Short/Long Answer questions | Q 33.2 | Page 78

Give reasons for the following Hammer drives a nail into the wood only when it is lifted up and then struck.

Short/Long Answer questions | Q 33.3 | Page 78

Give reasons for the following A horse and a dog are running with the same speed. Which one of them has more kinetic energy than the other.

Short/Long Answer questions | Q 33.4 | Page 78

Give reasons for the following A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.

Short/Long Answer questions | Q 34.1 | Page 78

State the energy changes in the following while in use An electric bulb.

Short/Long Answer questions | Q 34.2 | Page 78

State the energy changes in the following while in use An electric oven.

Short/Long Answer questions | Q 34.3 | Page 78

State the energy changes in the following while in use A loudspeaker .

Short/Long Answer questions | Q 34.4 | Page 78

State the energy changes in the following while using a microphone.

Short/Long Answer questions | Q 34.5 | Page 78

State the energy changes in the following while using an electric motor.

Numericals [Pages 78 - 79]

Selina solutions for Concise Physics Class 8 ICSE Chapter 4 Energy Numericals [Pages 78 - 79]

Numericals | Q 1 | Page 78

A force of 30 N acts on a body and moves it through a distance of 5 m in the direction of force. Calculate the work done by the force.

Numericals | Q 2 | Page 78

A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.

Numericals | Q 3 | Page 78

A body, when acted upon by a force of 10 kgf, moves to a distance 0.5 m in the direction of force. Find the work done by the force. Take 1 kgf = 10 N.

Numericals | Q 4 | Page 79

Two bodies of same masses are placed at heights h and 2h. Compare their gravitational potential energy.

Numericals | Q 5 | Page 79

Find the gravitational potential energy of 2.5 kg mass kept at a height of 15 m above the ground. The force of gravity on mass 1 kg is 10 n.

Numericals | Q 6 | Page 79

The gravitational potential energy stored in a box of weight 150 kgf is 1.5 x 104 J. Find the height of the box. Take 1 kgf = 10 N.

Numericals | Q 7 | Page 79

The potential energy of a body of mass 0.5 kg increases by 100 J when it is taken to the top of a tower from ground. If force of gravity on 1 kg is 10 N, what is the height of the tower?

Numericals | Q 8 | Page 79

A body of mass 60 kg is moving with a speed 50 m s_1. Find its kinetic energy.

Numericals | Q 9 | Page 79

A truck of mass 1000 kg, increases its speed from 36 km h-1 to 72 km h-1. Find the increase is its kinetic energy.

Numericals | Q 10 | Page 79

A car is moving with a speed of 15 km h-1 and another identical car is moving with a speed of 30 km h-1. Compare their kinetic energy.

Numericals | Q 11 | Page 79

A pump raises water by spending 4×105J of energy in 10s. Find the power of the pump.

Numericals | Q 12.1 | Page 79

It takes 20 s for a girl A to climb up the stairs while girl B takes 15 s for the same job. Compare the work done .

Numericals | Q 12.2 | Page 79

It takes 20 s for a girl A to climb up the stairs while girl B takes 15 s for the same job. Compare the power spent by then.

Selina solutions for Concise Physics Class 8 ICSE chapter 4 - Energy

Selina solutions for Concise Physics Class 8 ICSE chapter 4 (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 Concise Physics Class 8 ICSE solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Concise Physics Class 8 ICSE chapter 4 Energy are Types of Kinetic Energy, Definition of Work, Conversion of Potential Energy into Kinetic Energy, Transformation of Energy, Different Forms of Energy, Concept of Power, Kinetic Energy, Types of Potential Energy, Measurement of Work, Concept of Energy, Mechanical Energy and Its Different Form, Potential Energy, Factors Affecting the Power of a Source, Gravitational Potential Energy, Introduction of Work.

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