Tag: work and energy

Questions Related to work and energy

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

Show answer
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. $10^{-7} J$

Show answer
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

Show answer
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. $\displaystyle 1.8\times 10^{6}$

Show answer
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

Show answer
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

Show answer
Correct Option: D
Explanation:

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

What type of energy conversion takes place when a compressed spring is released?

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

  1. Molecular energy to potential energy

  2. Kinetic energy to potential energy

  3. Potential energy to kinetic energy

  4. Potential energy to molecular energy

Show answer
Correct Option: C

The negative of the work done  by the conservative internal forces on a system equals to the change in 

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

  1. total energy

  2. Kinetic energy

  3. Potential energy

  4. None of these

Show answer
Correct Option: C
Explanation:

The negative of the work done  by the conservative internal forces on a system equals to the change in potential energy


Hence, correct answer is option $C$

$1\  hp$ is equal to:

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

  1. $0.746\  kW$

  2. $7.46\  kW$

  3. $74.6\  kW$

  4. $746 \ kW$

Show answer
Correct Option: A
Explanation:

Horsepower (hp) is a unit of measurement of power (the rate at which work is done).A power level of 1 hp is approximately equivalent to $746$ watt (W) or $0.746$ kilowatt (kW).

The unit of work is joule $(J)$ in the $SI$ system and erg in the $CGS$ system. Find number of ergs in $1\ joule$.

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

  1. $10^{17} ergs$.

  2. $10^{9} ergs$.

  3. $10^{8} ergs$.

  4. $10^{7} ergs$.

Show answer
Correct Option: D