Tag: introduction to work and energy

Questions Related to introduction to work and energy

Rahul took a wooden cube of volume $1000  {cm}^3$ and put it in water. He observed that $\displaystyle \frac{3}{5}th$ of its volume is below the level of water. Later, he floated the cube in a liquid of density $0.8  g  {cm}^{-3}$ and applied extra force on the cube to completely submerge it in the given liquid. Calculate how much extra force Rahul applied on the cube.

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

  1. 2 N

  2. 8 N

  3. 6 N

  4. 4 N

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Correct Option: A

1 J is equal to

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

  1. ${10}^{5}$ erg

  2. ${10}^{7}$ erg

  3. ${10}^{-7}$ erg

  4. none of these

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Correct Option: B
Explanation:

$1 J=1N\times1m$


$={10}^{5}dyne\times{10}^{2}cm$

$={10}^{7}erg $

The c.g.s. unit of work is

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

  1. N

  2. dyne

  3. erg

  4. J

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Correct Option: C
Explanation:

The $c.g.s.$ unit of work is $erg.$

The $m.k.s.$ unit of work is $N$

One erg is equal to

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

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

  2. 1 Nm

  3. $10^7 J$

  4. $10^{-7}J$

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Correct Option: D

Select the correct statement for work, heat and change in internal energy

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

  1. Heat supplied and work done depends on initial and final states

  2. Change in internal energy depends on the initial and final states only

  3. Heat and work depend on the path between the two points

  4. All of these

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Correct Option: A

How many electron volts make one Joule?

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

  1. $ 3.25 \times 10^{19} \mathrm{eV} $

  2. $ 6.25 \times 10^{18} \mathrm{eV} $

  3. $ 9.25 \times 10^{17} \mathrm{eV} $

  4. $ 1.25 \times 10^{20} \mathrm{eV} $

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Correct Option: B

Water falls from a height of $210\, m$. Assuming whole of energy due to fall is converted into heat the rise in temperature of water would be 
($J = 4.3$ Joule/cal)

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

  1. $42^0\, C$

  2. $49^0\, C$

  3. $0.49^0\, C$

  4. $4.9^0\, C$

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Correct Option: C
Explanation:

$\begin{array}{l} \Delta \theta =0.0023h \ =0.0023\times 210 \ ={ 0.483^{ 0 } }C \ =\approx { 0.49^{ 0 } }C \end{array}$

Hence, Option $C$ is correct.

1 J Is equal to $1 : kg : m : s^{-2}$

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

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

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Correct Option: B
Explanation:

False
because,A Joule is equal$= Newton \times meter$, and a Newton $= mass \times acceleration$The unit for mass is kg and for acceleration is m${s}^{2}$. So if a Joule $=Newton \times meter$, it equals $kgm{s}^{2}times m$. The x meter makes the meter
on top squared so you get Joules $= kg{m^2}$${s}^{-2}$. 

Which of the following will give $1J$ of work?

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

  1. $F=1N,S=1m,\theta={0}^{0}$

  2. $F=1N,S=1m,\theta={90}^{0}$

  3. $F=0.1N,S=1m,\theta={0}^{0}$

  4. $F=0.1N,S=10m,\theta={90}^{0}$

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Correct Option: A
Explanation:

$W=F.S.cos\theta$
For $F=1, S=1, \theta={0}^{0}$, $W=1\times1{\times}cos{0}^{0}=1 J$

$4.0\times{10}^{-19}J=$

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

  1. $1eV$

  2. $2eV$

  3. $2.5eV$

  4. $5eV$

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Correct Option: C
Explanation:

$1eV=1.6\times{10}^{-19}J$


$\therefore{4.0}\times{10}^{-19}J=\dfrac{4.0\times{10}^{-19}}{1.6\times{10}^{-19}}eV=2.5eV$