Tag: introduction to work and energy

Questions Related to introduction to work and energy

Kilowatt hour (kWh) represents the unit of____

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. power

  2. impulse

  3. mementum

  4. none of these

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Correct Option: D
Explanation:

The kilowatt hour is a unit of energy equal to $3.6\times 10^6J$. If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is the power in kilowatts multiplied by the time in hours. so if kWh is unit of energy so none of the option is correct hence option D is the answer.

Watt sec represents the unit for:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. energy

  2. power

  3. force

  4. none of these

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Correct Option: A
Explanation:

A watt second (also watt-second, symbol W s or W. · s) is a derived unit of energy equivalent to the joule. The watt-second is the energy equivalent to the power of one watt sustained for one second.

So this is unit of energy.

One joule is approximately equal to:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. 0.28 cal

  2. 0.32 cal

  3. 0.24 cal

  4. 4.2 cal

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Correct Option: C
Explanation:

calorie (cal) is the energy needed to increase 1 gram of water by 1°C at a pressure of 1 atmosphere.

1 cal = 4.184 J. 
So 1J =0.24cal.

1 MeV is equal to:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. $1.6 \times 10^{-19} J$

  2. $1.6 \times 10^{-14} J$

  3. $1.6 \times 10^{-13} J$

  4. $1.6 \times 10^{13} J$

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Correct Option: C
Explanation:

 Electron volt (symbol eV) is a unit of energy equal to approximately 1.6×10−19  joules (symbol J). By definition, it is the amount of energy gained (or lost) by the charge of a single electron moving across an electric potential difference of one volt.

And mega electron volt (MeV) is $10^6\times eV$ so $1MeV=1.6 \times 10^{-13}$.
so best possible option is optionC.

The form of energy present in a wound spring is :

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. Chemical

  2. Heat energy

  3. Magnetic

  4. Mechanical

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Correct Option: D
Explanation:

no chemical reaction takes place while wounding a spring so no chemical energy.

no energy is stored in the form of temperature change so no heat energy is stored.
no magnetic field is around the spring so no magnetic energy.
but due to change in shape of the metal potential energy is stored, so answer is option D.

1erg is equal to:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. $ 1 g cm s^{-2}$

  2. 1 Nm

  3. $ 10^7 J$

  4. $10^{-7} J$

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Correct Option: D
Explanation:

An erg is the amount of work done by a force of one dyne exerted for a distance of one centimeter. In the CGS base units, it is equal to one gram centimeter-squared per second-squared

And joule is SI unit of work done or energy equals work done by force of 1N for a displacement of 1m.
So converting cgs to SI unit.
$1 erg= 10^{-3}N\times(10^{-2}m)^2\times1s$ $=10^{-7}$J.

A helicopter flying in the air has:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. only kinetic energy but not potential energy

  2. Only potential energy but not kinetic energy

  3. both potential and kinetic energy

  4. neither kinetic nor potential energy

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Correct Option: C
Explanation:

A flying helicopter has potential energy,mgh(mass by g by weight) and this potential energy does not depend in any way on how fast it is flying in a horizontal direction.

It also possesses kinetic energy at a constant velocity which is same at any height it flies.
The total energy is sum of both potential energy and kinetic energy.

One kilowatt-hour is equivalent to ______  joules.

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. $\displaystyle 3.6\times 10^{6}$

  2. $\displaystyle 6\times 10^{6}$

  3. $\displaystyle 3\times 10^{6}$

  4. $\displaystyle 1.8\times 10^{6}$

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Correct Option: A

The form of energy in presence of which other objects are seen is known as:

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. wind energy

  2. heat energy

  3. light energy

  4. chemical energy

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Correct Option: C
Explanation:

In presence of light energy, other objects are seen.

Which of the following is not a form of energy.

physics energy and its forms idea of energy introduction to work and energy work and energy

  1. Heat

  2. Light

  3. Sound

  4. Charge

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Correct Option: D
Explanation:

Charge is a fundamental property of matter. It is not a form of energy.