Tag: introduction to work and energy

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Multiple choice physics energy and its forms introduction to work work 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.

  1. 2 N

  2. 8 N

  3. 6 N

  4. 4 N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Volume = 1000 cm^3. In water (density 1), 3/5 submerged means weight = 0.6 * 1000 * 1 = 600g = 6N. In liquid (density 0.8), buoyant force when fully submerged = 1000 * 0.8 = 800g = 8N. Since weight is 6N, the extra force required to submerge it is 8N - 6N = 2N.

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

How many electron volts make one Joule?

  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} $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since 1 eV = 1.6 * 10^-19 Joules, the number of eV in 1 Joule is 1 / (1.6 * 10^-19), which equals 6.25 * 10^18.

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

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)

  1. $42^0\, C$
  2. $49^0\, C$
  3. $0.49^0\, C$
  4. $4.9^0\, C$
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient
Reveal answer Fill a bubble to check yourself
B Correct answer
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}$.