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Dear students, prepare for physics class 9th chapter 6 long questions. These important long questions are carefully added to get you best preparation for your 9th class physics ch. 6 exams.
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Our database contains a total of 0 questions for physics Short Questions. You’ll prepare using this huge databank.

Question: 1
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859781502982264113631">:</gwmw>5<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859781502982717626701">(</gwmw>A) Define potential energy. Give its examples and derive its equation P.E = <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859780804184387683050">mgh</gwmw>.
Answer: 1
Potential Eenergy :
The energy possessed by a body due to its position is known as its potential energy.
Stored water possesses potential energy due to its height . A hammer rasisedup to some height has the avilityto do word because it possesses potential energy. Astretchedbow has potential energy due itsStretched position. When released , the stored energy of the bow is called elastic potential energy
The potential energy possessed by a hammer is due to its height. The energy present in a body due to its height is called gravitational potential energy.
Let a body of mass m be raised up through height h from the ground. The body will acquire potential energy equal to the work done in lifting it to height h.
potential energy P.E = F x h
=w xh
= mg x h
P.E = mgh
Question: 2
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859789255065972988081">:</gwmw>(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.
Answer: 2
M= 200kg
h= 6 m
t= 10s
power of the pump = p=?
F= w
= mg
200 x 10
As we know that
p=w/t =F x s/t
But putting the values , we have
p= 2000 x6/10
P = 1200 W Ans
Question: 3
Q no: 6<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859792570062223490633">(</gwmw>A) Define efficiency. Write its formula.
Answer: 3
Efficiency 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.
Electric motors may be used to pump water, to blow air , to wash clothes, to drill holes, etc for that they use electricenergy. How good a machine is depends how much output we obtain from it by giving certain input .The ratio of useful output to input energy is very important to judge the working of machine
Mathematical form:
Efficiency =Required form of output/Total input energy x100
Question: 4
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859804933601555746541">:</gwmw>6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859805147401837075311"> ,</gwmw> if each step is 16 cm high.
Answer: 4
m= 50 kg
Height of h= 16 cm
each step = 0.16m
n= 25
t = 20s
p= ?
F = w
= mg
= 50 x 10
= 500N
Height = h= 0.16 x 25 = 4m
reached by man
As we know that
P =w/t = F x s/t
By putting the values
P= 500 x y/20
= 2000/20
= 100w Ans
Question: 5
Q no: 7<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859821278041911708633">(</gwmw>A) Write is the uses of Wind Energy.?
Answer: 5
Wind Energy:
Wind energy has used as a source of energy for centuries. It has powered sailing ships across the oceans . It has been used by windmills to grind grain and pump water. More recently , wind power is used to turn wind turbines. When many wind machines are grouped together on wind farms , they can generate enough power to operate a power plant. In the United stated , some wind farms generate more than 1300 MW of electricity a day. In Europe, many wind farms routinely generate hundred megawatts or more electricitya day
Question: 6
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859825816989941452392">:</gwmw>7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²
Answer: 6
Kinetic Energy :
The energy possessed by a body due to its motion is called kinetic energy.
Let a body of mass m is moving with velocity V. An opposing force F actingthrough a distance S brings it to rest. The body possesses kinetic energy and is capable to do work against opposing force F until all of its kinetic energy used up.
K.E of the body = Work done by it due to motion
K.E - FS
Vi = V
Vf =0
F = ma
a =-f/m
Since motion is opposed, hence , a is negative. Using 3rd equation of motion
2as =Vf² - Vi²
2 (-F/m)S =0² - V²
FS = +1/2 mv²
As we know that K.F is equal to the work done.
K.E =1/2 mv² ( proved )
Question: 7
Define work. when a force do work? explain
Answer: 7
Work: work is said to be done when a force acts on a body and moves it in the direction of the force.
Recognition of work: the question raised how much work is done? naturally, greater is the force acting on a body longer is the distance moved by it, larger would be work done
" work is done when a force acting on a body displaces it in the direction of force".
Question: 8
Define energy and explain kinetic energy
Answer: 8
Energy: the capability of doing work is called energy. A body is capable to do work only when it has energy.
Question: 9
Define potential energy, explain its types
Answer: 9
potential energy: the energy possessed by a body due to its position is called potential energy.
  • Stored water possesses the potential energy due to its height
  • A hammer raised up to some height has the ability to do work because it possesses potential energy
Question: 10
Explain different kind of energy
Answer: 10
Types of energy: there are number of forms of energy.
  • Mechanical energy: the energy of a body both due to its position or due to its motion is called the mechanical energy e.g.wind ,water running down in stream etc. possess mechanical energy.
  • Heat energy: The energy obtained due to burning of fuel is called heat energy. it obtained from the sun, or from the electric energy. It may also be obtained by burning of fuel. The main source of heat is the sun.
Question: 11
How is energy converted from one form to another? Give some examples
Answer: 11
Interconversion of energy: the conversion of one form of energy into another form is called interconversion of energy.
Explanation: energy cannot be destroyed however it can be converted into some other forms . For 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. In the process of rubbing mechanical energy is converted into heat energy. Processes in nature are the results of energy changes. For examples, some of the heat from the sun is taken up by water in the oceans. This increases thermal energy. Thermal energy causes water to evaporate from the surface to form water vapors. These vapors rise up and form clouds. As they cool down, they form water drops and fall down as rain. Potential energy changes to kinetic energy as the rain falls . This rain water may reach a lake or a dam. As the rain water flows down, its kinetic energy changes into thermal energy while parts of kinetic energy of flowing water is used to wash away soil particles of rocks known as soil erosion. During the interconversion of energy from one form to other forms, the total energy at any time remains constant .
Question: 12
What are fossil fuels? explain
Answer: 12
Fossil fuels: natural fuel such as coal, oil and gas are called fossil fuels because they are produced by dead bodies of lining things.
Uses; we use fossil fuels such as coal, gas to heat our houses and run industry. They are usually hydrocarbons.
Question: 13
What are nuclear fuels? explain it
Answer: 13
nuclear fuels: the materials through which we can obtain nuclear energy are called nuclear fuels uranium element. In nuclear power plants wee get energy as a result of fission reactions.
Question: 14
What is meant by renewable sources of energy?
Answer: 14
Renewable source of energy: the source of energy which wil not run out and can be used again and again are called renewable sources of energy
  • Energy from water
  • solar energy
  • wind energy
  • geothermal energy
  • energy from biomass
Question: 15
Write note on solar house heating and solar cells
Answer: 15
The use of solar energy is not new. However , it s use in houses and offices as well as the commercial industrial processes is quite recent. Complete solar house heating systems are successfully used in areas with a minimum amount of sunshine in water.
Parts: a heating system consists of
  1. A collector
  2. A storage device
  3. A distribution system
Question: 16
Explain the mass-energy equation
Answer: 16
Einstein 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 relation between mass m and energy E is given by Einstein's mas-energy equation
Where c is the speed of light( 3*108 ms-1)
Question: 17
Write and explain energy conversion processes involved in producing of electricity
Answer: 17
Steps of production of electricity from fossil fuels: we are using electricity in houses, offices, schools, business centers and in farms,. We have different ways of generating electricity. However, most of the electricity is obtained using fossil fuels such as oil, gas and coal. Fossil fuels are burnt in thermal power stations to produce electricity. Various energy conversion processes involved in producing electricity from coal are described follow
Question: 18
Write a note on energy a nd environment
Answer: 18
Sources; environmental problems such as pollution that consist of noise , air pollution and water pollution may arise by using different sources of energy such as:
  • Fossil fuels
  • Nuclear energy
Question: 19
What is energy converter ?
Answer: 19
Energy converter : an energy converter is a device in which a part of energy taken by the system is converted into useful work. Remaining energy is dissipated as heat energy, sound energy, noise into the environment
Question: 20
What is efficiency? explain working of an ideal system.
Answer: 20
Efficiency: efficiency 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: 21
Define power and explain its units
Answer: 21
Power is defined as the rate of doing work.
Power=P= work done / time taken