Tag: physics

Questions Related to physics

A vessel contains a mixture consisting of m$ _{1}$ - 7 g of nitrogen (M$ _{1}$ = 28) and m$ _{2}$ = 11 g of carbon dioxide (M$ _{2}$ = 44) at temperature T - 300 K and pressure P$ _{0}$ = 1 atm. The density of the mixture is

  1. $1.46g\ per\ litre$

  2. $2.567 g \ per \ litre$

  3. $3.752 g \ per \ litre$

  4. $4.572 g \ per \ litre$


Correct Option: A
Explanation:

Let the volume occupied $=V$

By Dalton's law of partial pressure
$\cfrac{P _{nit}}{P _0}=\cfrac{n _{nit}}{n _{nit}+n _{carb}}$
No. of moles of Nitrogen $\eta _{nit}=\cfrac{M _1}{M _{nit}}=\cfrac{7}{28}=0.25 mol$
No. of moles of carbon $\eta _{carb}=\cfrac{M _2}{M _{carb}}=\cfrac{11}{4}=0.25 mol$
Thus,
$P _{nit}=P _0\times\cfrac{0.25}{0.25\times0.25}=P _0/2=0.5atm$
From ideal gas equation
$V=\cfrac{nRT}{P}=\cfrac{0.25\times8.314\times290}{0.5\times101325}=0.0119mole$
Total mixture $m=(7+11)\times 10^{-11}kg$
Thus density s $P=\cfrac{m}{V}=\cfrac{(7+11)\times 10^{-3}}{0.0119}\approx1.46kg/m^3$
Option A is correct.

A vessel of volume V contains a mixture of $1$mole of hydrogen and $1$ mole of oxygen(both considered as ideal). Let $f _1(v)dv$ denote the fraction of molecules with speed between v and $(v+dv)$ with $f _2(v)dv$, similarly for oxygen. then

  1. $f _1(v)+f _2(v)=f(v)$ obeys the Maxwell's distribution law

  2. $f _1(v), f _2(v)$ will obey the Maxwell's distribution law separately

  3. Neither $f _1(v)$ nor $f _2(v)$ will obey the Maxwell's distribution law

  4. $f _2(v)$ and $f _1(v)$ will be the same


Correct Option: B
Explanation:

The Maxwell-Boltzmann speed distribution function $\left(N _v=\dfrac{dN}{dv}\right)$ depends on the mass of the gas molecule. [Here, dN is the number of molecules with speeds between v and $(v+dv)$]. The masses of hydrogen and oxygen molecules are different.

For satellite communication which wave is used?

  1. Space wave

  2. Sky wave

  3. Ground wave

  4. Microwave


Correct Option: A
Explanation:

A space wave travels in a straight line from transmitting antenna to the receiving antenna. Space waves are used for line of sight communication as well as satellite communication.

State whether the given statement is True or False :

Remote sensing is a technique of collection of information about an object, without a physical contact.

  1. True

  2. False


Correct Option: A
Explanation:

Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus it is in contrast to on site observation. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth.
Hence, the statement is true.

As the height of a satellite orbit gets lower, the speed of the satellite _________.

  1. decreases

  2. increases

  3. remains the same

  4. none of the above


Correct Option: B
Explanation:

$V=\sqrt { \cfrac { GMe }{ r }  } \ \therefore V\propto \cfrac { 1 }{ \sqrt { r }  } $

With decrease in $'r'$, velocity of satellite $increases$.

Let $R _s$ and $R _m$ be the distance of the geostationary satellite and moon from the center of earth. Then $\dfrac{R _m}{R _s}$ is

  1. $(29)^{1/2}$

  2. $(29)^{2/3}$

  3. $29$

  4. $(29)^{3/2}$


Correct Option: B

If the satellite is stopped sudden;y in its orbit which is at a distance radius of earth from earth's surface and allowed to fall freely into the earth. the speed with which it hits the surface of earth will be:

  1. $38,525 km/s$

  2. $1,525 km/s$

  3. $18,525 km/s$

  4. $28,525 km/s$


Correct Option: D

A remote -sensing satellite of earth revolves in a circular orbit at a height of $ 0.25 \times 10^6 $ m above the surface of earth. if earth's radius is $ 0.25 \times 10^6 $ m above the surface of earth. if earth's radius is $ 6.38 \times 10^6 m $ and $ g= 9.8 m/s^2 $, then the orbital speed of the satellite is :

  1. $6.67 km/s$

  2. $7.76 km/s$

  3. $8.56 km/s$

  4. $9.13 km/s$


Correct Option: A

What kind of battery used by older satellites?

  1. Lithium

  2. Leclanche

  3. Hydrogen

  4. Magnesium


Correct Option: C
Explanation:

Older satellite used $H-$ batteries.

State the chronological order in which the following events took place.
$1$. Launching of APPLE
$2$. Launching of Rohini
$3$. Antarctica expectation
$4$. Indian cosmonaut

  1. $2 - 1 - 3 - 4$

  2. $2 - 3 - 1 - 4$

  3. $3 - 1 - 2 - 4$

  4. $4 - 1 - 2 - 3$


Correct Option: D
Explanation:

a) Lunching of Apple - $1$ April, $1976$

b) Lunching of Rohini - $10$ Aug, $1979$
c) Indian cosmonaut - $1982$
(i.e. Rakesh Sharma, Indian air force pilot)
d) Antarctica expectation - $1965$
So, order is $d-a-b-c$.