Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

By sucking through a straw, a student can reduce the pressure in his lungs to $750 mm$ of Hg (density = $\displaystyle 13.6{ gm }/{ { cm }^{ 3 } }$). Using the straw, he can drink water from a glass upto a maximum depth of: 

  1. $10 cm$

  2. $75 cm$

  3. $13.6 cm$

  4. $1.36 cm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pressure difference created $= 10 mm$ of Hg 
This must be equal to the pressure of water column being created in the straw. If height of water column be $h$

$h \rho g = \dfrac{10}{10} \times 13.6 g$
$hg \times 1 = 13.6 g$
$h = 13.6 cm$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

One gram mole of oxygen is enclosed in a vessel at a temperature of $27$ and at one atmospheric pressure. The vessel is thermally insulated and is moved with a constant speed $u _0$. Calculate $u _0$ if the rise in temperature is $1K$ when the vessel is suddenly stopped?

  1. $35.6 m/s$

  2. $45 m/s$

  3. $90 m/s$

  4. $60 m/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

since internal energy depends only on the temperature ,

as the temperature changes,
the change in internal energy is
$\Delta U= \dfrac{nfR \Delta T}{2}$

vessel contains a gas of mass M,
change in kinetic energy $= \dfrac{nMv^2}{2}$

$\dfrac{nfR \Delta T}{2}$= $\dfrac{nMv^2}{2}$

$\dfrac{2}{\dfrac{c _p}{c _v} - 1}$

$f = \dfrac{2}{\dfrac{2}{5}}$ = 5

putting value

$v = 45 m/s$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

What will be the pressure in pascal due to a mercury column of $76$cm. Density of mercury is $13.6$ g$cm^2$, $g=980$ cm$s^2$?

  1. $1.0129\times 10^5$Pa

  2. $1.0129\times 10^4$Pa

  3. $1.0129\times 10^3$Pa

  4. $1.0129\times 10^2$Pa
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 h$=76cm$

Pressure=?

Formula to be used : $P=hgd$

Where h = height of mercury column and

 d= density of mercury$=13.6 gm/cc$

acceleration due to gravity$=980 cm/s²$

$P=hgd=13.6\times 980\times 76=1012928dyne.cm²$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

The height of the mercury column in a simple barometer is $h$. As the tube is inclined with the vertical at an angle $\alpha$, the length of the mercury column along the length of the tube will become:

  1. $h\cos{\alpha}$

  2. $\dfrac{h}{\cos{\alpha}}$

  3. $h\sin{\alpha}$

  4. $\dfrac{h}{\sin{\alpha}}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Similar to question 480419, the vertical height h is the projection of the length l along the tube, so h = l * cos(alpha), which means l = h / cos(alpha).

Multiple choice physics simple machine common machines terms related to machines introduction to simple machines

When the height of the inclined plane decreases :

  1. the mechanical advantage decreases

  2. the mechanical advantage increases

  3. effort increases

  4. it will not have any effect on the mechanical advantage
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The mechanical advantage of an inclined plane is given by length/height. As the height decreases, the ratio length/height increases, thus increasing the mechanical advantage.