Tag: concept of energy

Questions Related to concept of energy

When a body does some work its energy decreases. 

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

  1. True

  2. False

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Correct Option: A
Explanation:

When a body does some work it uses its energy to provide external force due to which its energy decreases.

Energy is the capacity to do work.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Definition of Energy “Capacity to do work”. If a ball falls due to free fall, its weight will do work, which is transferred to Kinetic Energy when dropped from a certain height. But then it says this is as 'energy is defined as the capacity to do work'

SI unit of energy is  _________ .

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

  1. newton

  2. joule

  3. erg

  4. metre

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Correct Option: B
Explanation:

Joule.

If the values of force and length are increased four times then the unit of energy will increases by?

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

  1. $4$ times

  2. $2$ times

  3. $8$ times

  4. $16$ times

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Correct Option: D
Explanation:

 Force is represented as $\left[ ML{ T }^{ -2 } \right] \quad and\quad length\left[ L \right] $

$energy\quad f\times d\quad is\left[ ML{ T }^{ -2 } \right] \quad \times \left[ L \right] =\left[ M{ L }^{ 2 }{ T }^{ -2 } \right] $
 if Force and length are quadrupled in value Energy
$4\left[ ML{ T }^{ -2 } \right] \quad \times 4\left[ L \right] =16\left[ M{ L }^{ 2 }{ T }^{ -2 } \right] $
unit increased by 16 times 

When a men walks on a horizontal surface  then work done by

physics work, energy and machines concept of energy energy for everything forms of energy

  1. friciton is zero

  2. contact force is non-zero

  3. gravity is non-zero

  4. None of these

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Correct Option: B
Explanation:

When the man moves on a horizontal surface, then work done by gravity is zero since gravitational force acts perpendicular to the displacement. 


And the normal force will be also perpendicular to displacement so work done by It also is zero. - - - - - - - - 1

But frictional force is acting opposite to displacement so work done by frictional force is negative. - - - - - - - - - - - 2

Using statement (1) and (2) we can say that work done by contact force is non - zero 


Energy can be defined as:

physics simple machines concept of energy energy for everything forms of energy

  1. The capacity to do work

  2. Work done in unit time

  3. A push or a pull

  4. Attraction between two oppositely charged particles

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Correct Option: A
Explanation:

Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, electrical, or other forms.

Flowing water has the capacity to do work

physics simple machines concept of energy energy for everything forms of energy

  1. True

  2. False

  3. Both

  4. None

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Correct Option: A
Explanation:

flowing water possess kinetic energy which is used to do work