Tag: introduction to work and energy

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

Kilowatt hour (kWh) represents the unit of____

  1. power

  2. impulse

  3. mementum

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

1 MeV is equal to:

  1. $1.6 \times 10^{-19} J$
  2. $1.6 \times 10^{-14} J$
  3. $1.6 \times 10^{-13} J$
  4. $1.6 \times 10^{13} J$
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

The form of energy present in a wound spring is :

  1. Chemical

  2. Heat energy

  3. Magnetic

  4. Mechanical
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

1erg is equal to:

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

  2. 1 Nm
  3. $ 10^7 J$
  4. $10^{-7} J$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

A helicopter flying in the air has:

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

One kilowatt-hour is equivalent to ______  joules.

  1. $\displaystyle 3.6\times 10^{6}$
  2. $\displaystyle 6\times 10^{6}$
  3. $\displaystyle 3\times 10^{6}$
  4. $\displaystyle 1.8\times 10^{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

One kilowatt-hour is the energy consumed by a 1 kW device in 1 hour. Since 1 kW = 1000 J/s and 1 hour = 3600 s, 1 kWh = 1000 * 3600 = 3.6 * 10^6 Joules.