The Class 8 Physics Chapter 4- Energy, deal with everything related to the topic of energy. Solve the Selina questions and compare it with ICSE Selina Class 8  Physics Chapter 4- Energy Solutions to find out how correct you are with your answers. These solutions from BYJU’S saves a lot of time and energy by providing all the necessary solutions for the question included in your ICSE syllabus.
Here is a brief of what you learn in this chapter.
The ability to do work is known as energy. The principle of conservation of energy states that energy can neither be created nor be destroyed. It can only be converted from one form to another. Know more about renewable and non-renewable sources of energy, find out the different methods to conserve the non-renewable energy resources like coal, petroleum, natural gas, nuclear energy by using renewable energy sources like solar energy, wind energy, ocean energy, geothermal energy and more about “Energy” by going through the chapter.
Download ICSE Class 8 Physics Selina Solutions PDF for Chapter 4 – Energy
A. Objective Questions
1. Write true or false for each statement
(a) A coolie does no work against the force of gravity while carrying luggage on a road
Answer: True.
(b) The energy stored in the water of a dam is the kinetic energy.
Answer: False.
(c) The energy of a flying kite is kinetic energy.
Answer: True.
(d) Work done by a boy depends on the time in which he does work.
Answer: False.
(e) Power spent by a body depends on the time for which it does work.
Answer: True.
Question 2.
Fill in the blanks:
(a) Work is said to be done by a forte only when the body moves.
(b) Work done = Force x distance moved in direction of force.
(c) The energy of a body is its capacity to do work.
(d) The S.I. unit of energy is the joule.
(e) The potential energy is due to its state rest of position and kinetic energy of the body is due to its state of motion.
(f) Gravitational potential energy U = mass × force of gravity on unit mass × height.
(g) Kinetic energy = ½ × mass × (speed)2
(h) Power P = work done/time taken.
(i) The S. I. unit of power is the watt
(j) I.H.P. = 746 W
Question 3.
Match the following:
Column AÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Column B
(a) A stone at a height                        (i) power
(b) A moving ball                            (ii) joule
(c) Energy                                  (iii) work done in 1 s
(d) Power                                  (iv) potential energy
(e) watt                                    (v) kinetic energy
Solution:
Column AÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Column B
(a) A stone at a height                    (iv) potential energy
(b) A moving ball                        (v) kinetic energy
(c) Energy                              (ii) joule
(d) Power                              (iii) work done in 1 s
(e) watt                                (i) power
Question 4.
Select the correct alternative
(a) The S.I. unit of work is
1. second
2. metre
3. joule
4. newton
Solution:Â The correct answer is 3. joule
(b) No work is done by a force if the body
1. moves in direction of the force
2. does not move
3. moves in the opposite direction
4. none of these
Solution:Â The correct answer 2. does not move
(c) Two coolies A and B do some work in time 1 minute and 2 minutes respectively. The power spent is
1. same by both coolies
2. is more by coolie A than by B
3. is less by coolie A than by B
4. nothing can be said.
Solution:Â The correct answer 2. is more by coolie A than by B
(d) The expression of power P is
1. P=mgh
2. P=P=1/2
3. P=F×d
4. P=F×d/t
Solution: The correct answer is 4. P=F×d/t
(e) 1 H.P is equal to
1. 1 W
2. 1 J
3. 746 J
4. 746 W
Solution:Â The correct answer is 4. 746 W
(f) When a boy doubles his speed, his kinetic energy becomes
1. half
2. double
3. four times
4. no change
Solution:Â The correct answer 3. four times
(g) A boy lifts luggage from height 2 m to 4 m. The potential energy will become
1. half
2. double
3. one-third
4. one-fourth
Solution:Â The correct answer 2. double
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