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Question what ways the solar energy get transformed into other forms of energy?explain.
2.what is meant by the law of conservation energy?explain. the energy of a freely falling body conserved?give the mathematical interpretation.
4.what is meant by power?what are the units of power?explain.
5.what are the commercial units of power?explain.

Hello saurav singh,

1. Green plants use the process of photosynthesis to convert sunshine to its own chemical energy. Solar cells convert sunshine into electrical energy. Sunshine gives the Earth thermal energy.

2. The various forms of energy are measured in Joules. Energy is often converted from one form of energy to another. Often in the real world, some of the energy is lost when there is an energy conversion taking place. The principle of conservation of energy suggests that 100% of one form of energy can be converted into energy in another form.

3. In the real world, no. A freely falling body will increase its speed and because of that the wind it faces will increase. The wind resists the increase of the body's speed. But often we can ignore the wind resistance because a falling body is not high enough above the ground to gain speed high enough to provide significant wind resistance. The shape of the falling body can decrease the wind's affect on the acceleration of the body.

The energy conversion taking place in the case of a falling body is gravitational potential energy converting to kinetic energy. The equation that expresses the conservation of energy during the conversion of gravitational potential energy to kinetic energy is
m*g*h = (1/2)*m*v^2
Using the principle of conservation of energy and knowing the initial gravitational potential energy, you can predict the speed the falling body will achieve. So ignoring slight losses of energy in a conversion of energy from one form to another is a useful tool.

4. An engine burning fuel unleashes the chemical energy in the fuel to do useful work. Remember that the unit that work is measured in is the Joule. Power is the amount of work, in Joules, that the engine can do per second. So power has the units Joules/second. This is useful information about the capability of the engine, so the combination of units Joule/second has been given a special name, the Watt. This was done to honor the physicist James Watt.

5. Power is measured in Watts in many situations. I don't understand what the question means by commercial units of power. Perhaps this is referring to horsepower as an alternative to the Watt. The horsepower should become an obsolete unit (along with the USA's pound and foot).

The Watt has become such a prevalent unit that it is used in some measurements of energy rather than using the Joule. Electrical energy used by the customers of a power plant is commonly measured in kiloWatt-hours. Remember that the Watt is equivalent to 1 Joule/sec. So 1 Watt.second is equal to 1 Joule. Some power companies record the customer's energy consumption in megajoules but the Watt-hour is more common.

I hope this helps,


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Steve Johnson


I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.


I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University

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