Tag: introduction to work and energy

Questions Related to introduction to work and energy

The force acting on a 4gm mass in the energy region ${ U=8x }^{ 2 }$ at x= -2 cm is :

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

  1. 8 dyne

  2. 4 dyne

  3. 16 dyne

  4. 32 dyne

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Correct Option: D
Explanation:

Given,

$m=4gm$
$U=8x^2$

The force acting on mass $m$ in the potential energy $U$  at $x=-2cm$ will be

$F=-\dfrac{dU}{dx}$
$F=-\dfrac{d(8x^2)}{dx}$
$F=-16x$
$|F| _{x=-2cm}=-16\times(-2)=32dyne$
The correct option is D.



Which of the following pairs represent units of the same physical quantity?

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

  1. kelvin and joule

  2. kelvin and calorie

  3. newton and calorie

  4. joule and calorie

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Correct Option: D
Explanation:

joule and calorie are both units of energy .
$1\  joule = 0.24 \ calories$

What is the equivalent of $1$ joule in calorie?

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

  1. $0.24$

  2. $2.4$

  3. $24$

  4. $240$

Show answer
Correct Option: A
Explanation:
$1 joule = 1/4.18 \ cal= 0.24 \ calorie$

Name the quantity which is measured in $Wh$.

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

  1. Force

  2. Power

  3. Energy

  4. All the above

Show answer
Correct Option: C
Explanation:

We know that $ power = work/ time$.

Power has unit $W$ and time can have either seconds or minutes or hours.Hence work can have either $W\ min$ or $Wh$ or $Ws$. We in general consider work is nothing but energy. Hence energy can have unit $Wh$.

A certain household has consumed $250$ units of energy during a month. How much energy is this in joule ?

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

  1. $9 \times 10^8:J $

  2. $10 \times 10^8:J $

  3. $9 \times 10^7:J $

  4. $9 \times 10^{-8}:J $

Show answer
Correct Option: A
Explanation:

Energy consumed in a month
$=250 : units = 250 : kWh$
$= 250 \times 3.6 \times 10^6 = 9 \times 10^8:J $

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. momentum

  4. none of these

Show answer
Correct Option: D
Explanation:

The kilowatt-hour ($kWh$) is a unit of energy equivalent to one kilowatt ($1\  kW$) of power expended for one hour ($1\  h$) of time.


State whether the given statement is True or False :
Kilowatt hour is the unit of power.
physics energy and its forms idea of energy introduction to work and energy work and energy

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

False
because,The kilowatt-hour (kWh) is a unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1 h) of time.

The commercial unit of measurement energy is 

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

  1. Watt -Hour

  2. Kilowatt

  3. Kilowatt hour

  4. Megawatt

Show answer
Correct Option: C
Explanation:

The commercial unit of measurement energy is Kilowatt hour.

The power supply in our home is measured in Kilowatt hour units.

$1\ kW$ is equal to :

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

  1. $1000\ watt$

  2. $10^{-3}\ mega\  watt$

  3. $A$ and $B$ both

  4. neither $A $ nor $B$

Show answer
Correct Option: C
Explanation:

$1000\ W= 1\ kW$
$1000 \ kW= 1\ MW$

The unit kWh represents

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

  1. power

  2. momentum

  3. energy

  4. force

Show answer
Correct Option: C
Explanation:

This is unit of energy.If the energy is being transmitted or used at a constant rate over a period of time, the total energy in kilowatt hours is the power in kilowatts multiplied by the time in hours.