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Question: 1
What is meant by efficiency of a system?
Answer: 1
1-118Efficiency of a system is the ratio of required form of energy obtained from a system as output to the total energy given to it as input.
Formula: Efficiency = Required form of output/total input energy
Question: 2
Define energy, give two types of mechanical energy.
Answer: 2
2-118A body possess energy if it is capable to do work.
Unit: Its unit is joule
Quantity: It is scalar quantity
Types of mechanical energy:
i. Kinetic energy ii. Potential energy
Question: 3
Define watt.
Answer: 3
3-118The SI unit of power is watt, One watt is power of a device which does 1 J of work in 1 sec.
1 Watt = 1 Js-1
Question: 4
Define potential energy, also give its formula.
Answer: 4
4-118The energy possessed by a body due to to position is called potential energy. There are two type of potential energy. .
Formula: P.E. = mgh
i. Elastic potential energy
ii.Gravitational potential energy.
Question: 5
When does a force do work? Explain.
Answer: 5
5-118When force acts on the body and body covers some distance in the direction of force then we said force do work.
Question: 6
Define work. What is its SI unit.
Answer: 6
6-118Work: work is done when a force acting on a body displaces it in the direction it in the direction of force.
W = Force x displacement
w= F.S
Unit: Its unit is newton meter or joule.
Question: 7
Define gravitational potential energy.
Answer: 7
7-118Gravitational potential energy possessed due to height of the body is called gravitational potential energy. G.P.E.= mgh
Example: The energy store in dam water.
Question: 8
Define Kinetic energy, also give its formula.
Answer: 8
8-118The energy possessed by a body due to its motion is called kinetic energy .
Formula: K.E.=1/2 mv2
Question: 9
Define Elastic potential energy.
Answer: 9
9-118Elastic potential energy: The energy possessed due to stretched position in a body is called elastic potential energy. It is stored potential energy in compressed spring.
Question: 10
Define unit of work.
Answer: 10
10-118Unit of work is joule.
Amount of work is one joule when a force of one newton displaces a body through one meter in the direction of force.
1 J = 1 Nm
Question: 11
What is meant by term power?
Answer: 11
11-118The rate of doing work is called power.
P = Work/time
Question: 12
Name the device that converts mechanical energy into electrical energy.
Answer: 12
12-118Generator is a device which converts mechanical energy into electrical energy.
Question: 13
State law of conservation of energy.
Answer: 13
13-118Energy can neither be created nor be destroyed but can be converted from one form in another .
Example; When we rub our band our muscular energy converts into heat energy.
Question: 14
What is photo cell?
Answer: 14
14-118A solar cell also called photo cell is made from silicon wafer. When sunlight falls on a solar cell. It converts the light directly into electrical energy.
Question: 15
Write the bigger units of power.
Answer: 15
15-118Bigger units of power are kilowatt , megawatt, horse power.
Question: 16
Define Elastic potential energy and give its example.
Answer: 16
16-118Elastic Potential Energy:
The energy present in the stretchedbow is called elastic potential energy. A stretchedbow has potential energy due to its stretched position
Question: 17
Give a example of the renewable energy source.
Answer: 17
17-118Sun light and water power are renewable energy source.
Question: 18
Write down the name of two nuclear reactions.
Answer: 18
18-118Fission and Fusion are two major reactions which give out nuclear energy.
Question: 19
How can you find the efficiency of system
Answer: 19
19-118Efficiency of a system is the ratio of required form of energy obtained from a system as output to the total energy given to it as input
We can find the efficiency of a system by following formula
Question: 20
What is meant by bio mass energy?
Answer: 20
20-118Biomass is plant or animal wastes that can be that can be burnt as fuel. Other forms of biomass are garbage, farm wastes, sugarcane and other plants. The energy obtained from biomass is called biomass energy.
Question: 21
Define mechanical energy.
Answer: 21
21-118Energy in required form obtained from a working system is always less than the energy give to it as input. Because every system meet energy losses due to friction in the form of heat, noise etc.
Question: 22
What are effects of fossil fuels on human health?
Answer: 22
22-118It causes serious health problem such as headache, tension, nausea, allergic reaction and irritation of eyes. nose and throat.
Question: 23
How a pole vaulter acquired changes of energy?
Answer: 23
23-118Pole culture is capableto store all the vaulter's Kinetic energy while bending in the form of potential energy.
Question: 24
Name the five devices that convert electrical energy into mechanical energy.
Answer: 24
24-1181- Electric Motor
2- Electric Fan
3- Elevator
4- Drill machine
5- Grinder Sewing machine
Question: 25
What are solar panels.
Answer: 25
25-118Large number of solar cells are wired together to form solar panels
Question: 26
A cyclist does 12 joules of useful work while pedaling his bike from every 100 joules of food energy which he takes. What is his efficiency?
Answer: 26
26-118 W= 12J
E= 100 J
Efficiency = 12J/100J
= 0.12
% Efficiency = 0.12 x100
= 12%
Question: 27
Give the uses of solar cells.
Answer: 27
27-118Solar cells are used in calculators, watches and toys.
Question: 28
Write uses of energy, pollute our environment?
Answer: 28
28-118Burning of fuel and solid wastes in homes, automobiles and factories release harmful amounts of air pollutants
2- Nuclear power plants do not produce carbon dioxide, but they produce dangerous radioactive waste
Question: 29
On which parts solar house heating system consist of
Answer: 29
29-118A collector
A storage device
Distribution system
Question: 30
How solar energy can be converted directly into electricity?
Answer: 30
30-118Solar energy can be converted directly into electricity by solar cells.
Question: 31
Define energy give two types of mechanical energy
Answer: 31
31-118Energy: A body possesses energy if it is carpetable to do work
Question: 32
How much work is done when a body moves with uniform velocity?
Answer: 32
32-118When a body moves with uniform velocity means moving with zero acceleration then work done will be zero
Question: 33
What is Magma?
Answer: 33
33-118In some parts of world,the Earth provided us hot water from geyser& hot spring there is hot molten part, deep in earth called magma.
Question: 34
Define work. Write formula and unit.
Answer: 34
34-118Work:
Work is done when a force acting on a body displaces it in the direction of a force
Work done = force x displacement
W= FS
Question: 35
Mechanical energy converts into heat energy tive its example.
Answer: 35
35-118Mechanical energy converts into heat energy.
Example: Rub your hands together quickly . You will feel them warm. You have used your muscular energy in rubbing hands as a result heat is produced.
Question: 36
What is meant by bio mass energy
Answer: 36
36-118Bio Mass: Biomass is plant or animal wastes that can be burnt as fuel Other forms of biomass are garbage, farm wastes, sugarcane and other plants. The energy obtained from biomass is called biomass energy
Question: 37
Define Potential energy and write its formula.
Answer: 37
37-118Potential Energy:
The energy possessed by a body due to its position is known as its potential energy P.E = mgh
Question: 38
A body of mass 50 kg is raised to a height of 3m what is its potential energy?
Answer: 38
38-118 P.E = Mgh
= 3 x10 x 50
P.E = 1500
Question: 39
When does a foce do work
Answer: 39
39-118When foce acts on the body and body covers some distance in the direction of force then we said force do work
Question: 40
Define potential energy and write its formula
Answer: 40
40-118Potential energy: The energy possessed by a bogy due to tis position is known as its potential energy
Question: 41
Define kinetic EnergyWrite its equation
Answer: 41
41-118Kinetic Energy:
The energy possessed by a body due to its motion is called its kinetic energy.
K.E =1/2 mv²
Question: 42
Define potential energy also give its formula
Answer: 42
42-118Potential Energy: The energy possessed by a body to do work due to position is called potential energy There are two type of potential energy
Question: 43
How much power is used by a 40Kg athleteby climbing 10m high ladder in 10s
Answer: 43
43-118 F= w
F= mg
F= 4 x 10
F= 400N
Question: 44
What is meant by effieciency of a system
Answer: 44
44-118Efficiency of a system is the ration of required form of energy obtained from a system as output to the total energy given to it as input
Question: 45
Differentiate between mechanical and chemical energy
Answer: 45
45-118Mechanical Energy: The energy possessed by a body both due to its motion or position is called mechanical energy moving car wind lifted hammar posses mechanical energy
Question: 46
What is meant by term power
Answer: 46
46-118The rate of doing work is called power
Question: 47
Why fossil fuels are called non- renewable source of energy?
Answer: 47
47-118Fossil fuels are called non renewable source of energy because they will run out like coal, oil and gas.
Question: 48
Define Walt
Answer: 48
48-118Walt The SI unit of power is Walt One Watt is power of a device which does 1 j of work in 1 sec
Question: 49
Define kinetic energy also give its formula
Answer: 49
49-118The energy possessed by a body due to its motion is called kinetic energy
Question: 50
What are the major sources of energy?
Answer: 50
50-118Major sources of energy are as following .
1-Fossil fuels
2-Nuclear Fuels.
Question: 51
Write two uses of wind energy
Answer: 51
51-118Uses of wind energy
Wind energy has powered sailing ships across the oceans
Wind energy has been used by windmills to rind grain and pump water
Question: 52
Define unit of work
Answer: 52
52-118Unit of work is joule (J)
Amount of work is one joule when a force of one newton displace a body through one meter in the direction of force
Question: 53
Why do we need energy
Answer: 53
53-118Energy: A body possesses energy if it is capable to do work
Question: 54
How is energy converted from one form to another
Answer: 54
54-118Energy can be converted from one from to another form For example heat energy is converted into mechanical energy and electrical energy can be converted into light energy
Question: 55
Why output energy is always less than the input energy
Answer: 55
55-118The energy in required form obtained from a working system is always less than the energy given to it us input Because every system meet energy losses due to friction in the form of heat noise etc
Question: 56
Give example of the renewable energy source
Answer: 56
56-118Sun light and wither power are renewable energy sources
Question: 57
Which form of energy is most preferred and why
Answer: 57
57-118Solar energy is preferred to others.
Question: 58
Why fossil fuels are called non-renewable form of energy
Answer: 58
58-118The fossil fuels are one used to get energy that are consumed completely and these took millions of year for their formation So these are no renewable.
Question: 59
Write the uses of wind energy
Answer: 59
59-118Use of Wind Energy: Wind energy is used as a source of energy for centuries
It has been used by windmills to grind grain and pump water It is also used to turn wind turbines.
Question: 60
What is magma
Answer: 60
60-118Magma In some parts of world, the Earth provided us hot water from geyser hot spring There is hot molten part deep in earth called magma.
Question: 61
Define elastic potential energy
Answer: 61
61-118The energy possessed due to stretched position in a body is called elastic potential energy. It is stored potential energy in compressed spring
Question: 62
A crate is moved by pulling, with mass the attached to it.
Answer: 62
62-118Given Date: F=100 N
S =10M
Question: 63
Prove that
Answer: 63
63-118P=W/t
P=f.s/t
P=F.v
Question: 64
Name the five devices that convert electrical energy into mechanical energy
Answer: 64
64-118The electrical energy is converted into mechanical energy by
Electrical motor
Drill machine
Electric fan
Grinder
Elevator
Question: 65
How nuclear energy is obtained
Answer: 65
65-118Nuclear Energy: It is a form of energy which is released from the nucleus due to nuclear reactions such as fission or fusion reactions
Question: 66
State law of conservation of energy
Answer: 66
66-118Law of Conservation of Energy: Energy can neither be created nor be destroyed but can be converted from one form to another
Question: 67
What is soil erosion
Answer: 67
67-118As the rain water flows down its kinetic energy changes into thermal energy while parts of the kinetic energy of following water is used to wash away soil particles of rocks known as soil erosion.
Question: 68
What is photo cell
Answer: 68
68-118A solar cell also called photo cell is made from silicon wafer. When sunlight falls on a solar cell it converts the light directly into electrical energy.
Question: 69
Define mechanical energy
Answer: 69
69-118Mechanical Energy: Energy possessed by a body both due to its motion or position is called mechanical energy it has two types
Kinetic energy
Potential energy
Question: 70
What is meant by chemical energy
Answer: 70
70-118Chemical Energy: The energy released from substances during chemical reactions is called chemical energy
Question: 71
Define chemical energy and write one method to obtain it
Answer: 71
71-118Chemical Energy: Energy produce during chemical reactions is called chemical energyMethod to Obtain it: Burning of coal, natural gas and wood in arit is chemical reaction which release energy as heat and light.
Question: 72
When does a force work
Answer: 72
72-118In physics, work is done when a force acts on a body and moves it in the direction of the force
Question: 73
Write down the name of two nuclear reactions
Answer: 73
73-118Fission and fusion are two major reactions which give out nuclear energy
Question: 74
Write names of two renewable energy sources
Answer: 74
74-118Name of renewable energy sources are
Energy from water, Energy from the sun, Biomass, Wind energy, Geothermal energy sources.
Question: 75
Mechanical energy converts into heat energy give its example
Answer: 75
75-118Mechanical energy converts into heat energy
Example: Rub your hands together quickly You will feel them warm You have used r muscular energy in rubbing hands as a result heat is produced
Question: 76
What is difference between kinetic Energy and potential Energy
Answer: 76
76-118Kinetic Energy: The energy possessed by a body due to its motion is called its kinetic energy.
Kinetic energy is represented by k.e
Question: 77
Write the bigger units of power
Answer: 77
77-118Bigger Units bigger units of power: Bigger of power are kilowatt (kw), megawatt (MW) horse power The relation between them is as follow
Question: 78
What is meant by Nuclear Energy
Answer: 78
78-118Nuclear Energy: Energy released in various nuclear reactions like fission and fusion reaction is called nuclear energy
Question: 79
Write equation for K.E and P.E
Answer: 79
79-118Kinetic energy: K.E 1/2
Where m is mass and v is velocity of body
Question: 80
How solar energy can be converted directly into electricity
Answer: 80
80-118Solar energy can be converted directly into electricity by solar cells
Question: 81
Mechanical energy can be converted in heat energy
Answer: 81
81-118Explain with an example: By rubbing hands quickly these will be warmed Its means b rubbing hand muscular energy is used and as a result heat is produced, In this process of rubbing hands mechanical energy is converted into heat energy
Question: 82
How Biomass is used to obtain energy
Answer: 82
82-118There are different ways to get energy from biomass Some of these are as follow
Different forms of biomass are used to run power plants.
Many Industries that use forest products get half of their electricity by burning Burk and other wood wastes electricity by burning Burk and other wood wastes
Plants and animal wastes can be burnt as fuel
Question: 83
Define Work and Joule
Answer: 83
83-118Work: Work is done when a force acting on a acting on a body displace it in the direction of a force
Question: 84
What are effects of fossil fuels on human health
Answer: 84
84-118It causes serious health problem such as headache, tension, nausea, allergic reaction and irritation of eyes, nose and throat.
Question: 85
What is the second name of solar cell and how it made
Answer: 85
85-118A solar cell also called photo cell. Solar cell made from silicon wafer. When sunlight falls on a solar cell, it converts the ight directly into electrical energy Solar cells are soused calculators, watches and toys.
Question: 86
How is energy produced from nuclear fuels
Answer: 86
86-118The energy is produces from nuclear fuels by nuclear reactions such as fission and fusion reactions.
Question: 87
Give purposes of solar panels
Answer: 87
87-118Solar panels can provide power to telephone booths, light house, scientific research centres and satellites.
Question: 88
Name such a device that converts mechanical energy into electrical energy
Answer: 88
88-118Generator is a device that converts mechanical energy into electrical energy
Question: 89
Give the use of solar cell
Answer: 89
89-118Solar cells are used in calculators watches and toys.
Question: 90
What is meant by Geothermal energy
Answer: 90
90-118Geothermal energy: In some part of word the Earth provides us hot water from geysers and hot springs There is hot molten part deep in the Earth is called magma. Water reaching close to the magma changes to steam due to high temperature of megma This energy is called geothermal energy
Question: 91
Define mechanical energy and write its types
Answer: 91
91-118Mechanical energy: The energy possessed by a body both due to its motion or position is called mechanical energy
Question: 92
What are solar panels
Answer: 92
92-118Large number of solar cells are wired together to form solar panels
Question: 93
What is meant by Energy from Biomass
Answer: 93
93-118Biomass is plant or animal wastes also when animal during dead plants and dead animal decompose, they give off a mixture of methane and carbon dioxide. Electricity can produce by burning methane.
Question: 94
What two sources of non-renewable energy
Answer: 94
94-118Non-renewable: Those sources of energy which finish with continous use of these source are called source of non-renewable energy
Fossil fuels,Nuclear fuels
Question: 95
Define Energy
Answer: 95
95-118Energy Ability of a body to do work is called energy
Question: 96
Write brief note on Einstein mass energy equation
Answer: 96
96-118Einstein predicted the interconversion of matter and energy. According to him, a loss in the mass of a body provides a lot of energy This happen in the nuclear reaction The reaction between the mass m and energy E is given by Einstein's mass energy equation
The above equation shows that tremendous amount of energy can be obtained from small quantity of matter It happens that matter is a highly concentrated form of energy
Question: 97
Write names of two non-renewable and renewable sources of energy
Answer: 97
97-118Non renewable sources of energy are
Fossil fuels
Nuclear fuels
Renewable source of energy are
solar energy, Wind energy
Question: 98
Define work and energy
Answer: 98
98-118Work: Work is said to be done when force acting on a body displaces it in the direction of the force.
Question: 99
Write two disadvantages of thermal pollution
Answer: 99
99-118Thermal pollution upsets the balance of lift
Thermal pollution endanger the survival of many species.
Question: 100
Write down the two disadvantages of fossil fuels
Answer: 100
100-118Fossil fuels release harmful waste products. These wastes include carbon mono-oxide and other harmful gases which pollute the environment
Long espouse of these harmful gases may cause as the mas, lungs, cancer, heart diseases and even damage to bran, nerves and other organs of our body.
This causes serious health problems such as headache, Tension, nausea, allergic reactions, irritation of eyes, nose and throat.
Question: 101
On which factor work depends
Answer: 101
101-118Work: Work is done when a force acting on a body displaces in the direction of force
Formula: it is a scalar quantity
Question: 102
Where and why catalytic converter is to be used
Answer: 102
102-118New cars have catalytic converters, These devices convert some polluting gases.
Question: 103
Differentiate between electrical energy and light
Answer: 103
103-118Electrical Energy: Electricity is one of the widely used form of energy
Electrical energy can be supplied through wires easily to any desired place
Electrical energy can get from batteries and electric generators.
Question: 104
Define fission reaction
Answer: 104
104-118Fission reaction: Nuclear fussion is the process in which a large nucleus splits into smaller nuclei with the release of energy
Question: 105
Define kinetic energy and write tis equation
Answer: 105
105-118Kinetic energy: The energy possessed by a body due to its motion is called its kinetic energy
Education K.E=1/2
Question: 106
Name two devices that convert electrical energy into mechanical energy
Answer: 106
106-118D.C motor and Electrical fane are those devices which convert electrical energy into mechanical energy
Question: 107
Define heat energy
Answer: 107
107-118Heat Energy: A form of energy given out by hot bodies is called heat energy
Question: 108
Differentiate between solar cell and solar penal
Answer: 108
108-118Solar Cell: Solar cell is made up from silicon water
Solar cells are used in calculators watches and toys.
Question: 109
Write the names of major sources of Energy
Answer: 109
109-118Major Source of Energy
Fossil fuels, Nuclear fuels, Sun, Water
Question: 110
How do we gain energy from air
Answer: 110
110-118Wind has power sailing ships across the oceans It has been used by windmills to grind grain and puop water Now wind power is used to turn wind turbines. When many wind machines are grouped together on wind forms they generate enough power to operator a power plant
Question: 111
Differcreate between Mechanical energy and Sound energy
Answer: 111
111-118Mechanical Energy: energy possessed by a body due to its motion or change in position is called mechanical energy
Question: 112
Define geothermal energy and elastic potential energy
Answer: 112
112-118Geothermal Energy: There is hot molton part, deep in the earth called magma water reaching close to the magma charges to steam due to the high temperature of magma This energy is called geothermal energy This energy can be utilized by drilling deep in the earth
Question: 113
Write the mass energy equation and value of speed of light
Answer: 113
113-118Mass Energy Equation: The Einstein's mass-energy equation states that mass and energy are interconvertible to each other
Question: 114
Define efficiency and write its equation
Answer: 114
114-118Efficiency: Efficiency of a system is the ratio of required form of energy obtained from a system as output to the total energy give to it as input
Question: 115
On what parts a heating system consist of
Answer: 115
115-118A heating system consists of the following factors
A collector, A storage device, A distribution system
Question: 116
Define power and watt
Answer: 116
116-118Power: The rate of doing work
Question: 117
Write down two ases of thermal pollution.
Answer: 117
117-118Global warming is the major causes of thermal pollution. The heat produced bby fission reaction causes thermal polution.
Question: 118
To construct such a working system whose efficiency is 100% is impossible Why
Answer: 118
118-118To construct such a working system, whose efficiency is 100% is impossible because every system meets energy losses due to friction that causes heat, noise etc These are not the useful form of energyh and go waste.
