Tag: concept of energy

Questions Related to concept of energy

Erg is a unit for :

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. Energy

  2. Work

  3. Force

  4. Velocity

Show answer
Correct Option: A
Explanation:

Erg is a unit of Energy.

The capacity to do work is called:

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. Energy

  2. force

  3. motion

  4. speed

Show answer
Correct Option: A
Explanation:

Energy is defined as the capacity to do work.

$1calorie=$

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $4180J$

  2. $4.18J$

  3. $0.418J$

  4. none of these

Show answer
Correct Option: B
Explanation:

$1calorie=4.18J$

$1kWh=$

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. ${3.6}\times{10}^{4}J$

  2. ${3.6}\times{10}^{5}J$

  3. ${36}\times{10}^{6}J$

  4. None of these

Show answer
Correct Option: D
Explanation:

$1kWh=1kilowatt{\times}1hour=1000{J}{s}^{-1}\times{3600}s=3.6\times{10}^{6}J$
So, none of option A, B and C are correct.

The amount of work done (or, energy spent) by a source of power $1kW$ in $1h$ time is:

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $1J$

  2. $1Wh$

  3. $1kWh$

  4. $1calorie$

Show answer
Correct Option: C
Explanation:

$1kWh$ is the amount of work done (or, energy spent) by a source of power $1kW$ in $1h$ time.
So, ${1kW}\times{1h}=1kWh$

An object of mass $40\ kg$ is raised to a height of $5\ m$ above ground. If the object is allowed to fall down find its kinetic energy when it is half-way down.

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. 1960 J

  2. 980 J

  3. 990 J

  4. 1000 J

Show answer
Correct Option: B
Explanation:

Gravitational Potential energy, $W = mgh$

$h=$ vertical displacement $=5\ m$

$m =$ Mass of object $= 40\ Kg$

$g =$ Acceleration due to gravity $= 9.8\ ms^{-2}$

$W = 40 \times 5 \times 9.8= 1960\ J$

For half way down$=\dfrac{1960}{2}= 980\ J$

At this point i.e. half way object has an equal amount of potential and kinetic energy.

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

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $9 \times 10^{10}\ J$

  2. $9 \times 10^{8}\ J$

  3. $9 \times 10^{9}\ J$

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

Show answer
Correct Option: B
Explanation:

$1$ unit of energy $=1\ kWh$

$1\ kwh=3.6 \times 10^{6}\ J$

Thus $250$ unit$=250 \times 3.6 \times 10^{6}\ J$$=9 \times 10^{8}\ J$

Which of the following is NOT a measure of energy?

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $J s$

  2. $W s$

  3. $kWh$

  4. $erg$

Show answer
Correct Option: A
Explanation:
Power is defined as work done per unit time and the unit of work/energy is Joules per second which is termed as Watt and Watt is the unit of Power
Hence Js is  not a measure of energy.

Identify the best definition of energy?

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. anything that has mass and takes up space

  2. distance moved in a period of time

  3. ability to do work

  4. mode of opperation

  5. moment of an object with application of force

Show answer
Correct Option: C
Explanation:

Energy is defined as the ability to do work and its SI unit is Joule.

Energy equivalent of 4.2 mg in kilo calories is

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $9 \times 10^{10} cal$

  2. $8 \times 10^{8} cal$

  3. $10 \times 10^{9} cal$

  4. $6 \times 10^{7} cal$

Show answer
Correct Option: A