Tag: physics

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

kg $m^2S^{-2}$ represents the unit of :

  1. kinetic energy only

  2. work done only

  3. potential energy only

  4. all the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Work done is same as energy which is measured in joules. 1 joule is same as 1 newton expanded over 1 meter which is force multiplied by distance.

Force is defined as mass into acceleration. Hence if we accelerate 1kg mass by 1m/s$^{2}$ in a straight line for a distance of 1 meter, we have indirectly expanded 1 joule of energy .
Also acceleration is distance per second squared.
Thus we have mass $\ast$ acceleration $ast$ distance which is Kg m$^{2}$ S$^{-2}$.

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

A body at rest can have:

  1. speed

  2. energy

  3. momentum

  4. velocity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If a body is at rest then its position does not changes if position is not changing then $\frac{dx}{dt}=0$ so velocity is zero.

If Instantanious velocity is zero then speed is also zero this means if speed is zero then kinetic energy is also zero.
If v=0 then mv=0 i.e. momentum is also zero.
But a body raised upto some height against gravity and is at rest but it poses some potential energy which when released will be converted to kinetic energy.
So a body at rest can poses only potential energy from all these options.

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

A man carries a heavy box on his head on a horizontal plane form one place to another. In this he does

  1. Maximum work

  2. No work

  3. Negative work

  4. Minimum work
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Work is defined as force multiplied by displacement in the direction of the force. When carrying a load horizontally, the force (gravity) acts vertically, while the displacement is horizontal. Since the angle between force and displacement is 90 degrees, the work done is zero.

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

$1eV=$

  1. $16\times{10}^{-19}J$
  2. $1.6\times{10}^{-19}J$
  3. $1.6\times{10}^{19}J$
  4. $1.6\times{10}^{-19}erg$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$1eV$ is the energy gained by an electron when it is accelerated through a potential difference of $1volt$.
So, $1eV=$ charge of an electron $\times$ $1volt$ $=1.6\times{10}^{-19}coulomb$ ${\times}1volt=1.6\times{10}^{-19}J$