Tag: physics

Questions Related to physics

Temperature of $1\ mole$ of a gas is increased by $2^ {o}C$ at constant pressure, work done is

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. $R$

  2. $2R$

  3. $R/2$

  4. $3R$

Show answer
Correct Option: B
Explanation:

$W = nR\Delta T$

$ = 1\,molRJ\,{K^{ - 1}}\,mo{l^{ - 1}}\,2K$
$ = 2R\,\,joules$
Hence,
option $(B)$ is correct answer.

Air is pumped into an automobile tube upto a pressure of $200 \mathrm{kP}  $ in the morning when the air temperature is $  22^{\circ} \mathrm{C}  $ . During the day, temperature rises to $ 42^{\circ} \mathrm{C}  $ and the tube expands by $2 \%  $ . The pressure of the air in the tube at this temperature, will be approximately

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. $212 \mathrm{kPa} $

  2. $209 k P a $

  3. $206 \mathrm{kPa} $

  4. $200 \mathrm{kPa} $

Show answer
Correct Option: B
Explanation:

$\begin{array}{l} Given\, \, { P _{ 1 } }=200\, \, k\, pa \ { T _{ 1 } }=22^{ \circ  }C=273+22-295K \ { T _{ 2 } }=42^{ \circ  }C=273+42=315K \ PV=nRT \ \left( { \dfrac { { PV } }{ T }  } \right) ={ { constant } }\left[ \begin{array}{l} { { Since } }\, \, number\, \, of\, \, moles \ and\, \, R\, \, are\, \, { { constant } } \end{array} \right]  \ \dfrac { { { P _{ 1 } }{ V _{ 1 } } } }{ { { T _{ 1 } } } } =\dfrac { { { P _{ 2 } }{ V _{ 2 } } } }{ { { T _{ 2 } } } }  \ \dfrac { { 200\times 1 } }{ { 295 } } =\dfrac { { { P _{ 2 } }\left( { 1.02 } \right)  } }{ { 315 } }  \ { P _{ 2 } }=\dfrac { { 200\times 315 } }{ { 295\times 1.02 } } \, \, kPa \ = 209\, \, kPa \end{array}$

Option B.

A person blows into open-end of a long pipe. As a result, a high pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe,

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. a high pressure pulse starts traveling up the pipe, it the other end of the pipe is open.

  2. a low pressure pulse starts traveling up the pipe, if the other end of the pipe is open.

  3. a low pressure pulse starts traveling up the pipe, if the other end ot the pipe is closed.

  4. a high pressure pulse starts traveling up the pipe, if the other end of the pipe is closed.

Show answer
Correct Option: D
Explanation:

A pressure wave undergoes a phase change of $ \pi$ radians on 

reflection from open end of no phase change occurs on reflection from 
closed end.

Which of the following are units used to measure pressure?

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. $kg$ ${m}^{-2}$

  2. pascal (Pa)

  3. newton per ${m}^{2}$

  4. joules

Show answer
Correct Option: B,C
Explanation:

The pressure is the force per unit area. So, $P=F/A$

The unit of force is newton (N) and unit of area is $m^2$. 
Thus, the unit of pressure is $N/m^2$. 
Pascal is the SI unit of pressure. It is equal to one newton divided by one square meter. 

The SI unit of pressure is $N/m^2$.This unit is otherwise called ____________.

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. Pascal

  2. Newton

  3. Joule

  4. None of these

Show answer
Correct Option: A
Explanation:

Pressure is defined as force applied per unit area. Hence, its SI unit is $N/{ m }^{ 2 }$ or Pascal here,

         1 Pascal = 1 $N/{ m }^{ 2 }$.

Two women are of the same weight. One wears sandals with pointed heels while the other wears sandals with flat soles. Which one would feel more comfortable while walking on a sandy beach?

physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

  1. The one with pointed heels

  2. The one with flat soles

  3. Both will feel similar comfort

  4. Can't say

Show answer
Correct Option: B
Explanation:

Pressure(P)$=$$ \frac{Force(F)}{Area(A)}$

As both the women have same weight, so both of them will apply the same force on the ground. But flat soles having larger area compared to sandals with pointed heels, will exert lesser pressure compared to that of sandals having pointed heels. So, the sandals with pointed heels will sink more. Therefore, the woman having flat sole sandal will feel more comfortable while walking on a sandy beach.

Why do we sprinkle powder before playing carroms?

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. To increase friction

  2. To decrease friction

  3. To increase or decrease the friction depending on the type of the game played

  4. None of these

Show answer
Correct Option: B
Explanation:

It is done just to reduce the friction. On microscopic level, the powder particles offer rolling friction to the striker because of which the striker can be rolled around smoothly.

State whether the statements are true or false:
Oil is used to reduce the friction on door hinges.

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Lubrication is another way to make a surface smoother. A lubricant is a slippery substance designed to reduce the friction between surfaces, Since the door hinges are exposed to the atmosphere the chances of corrosion increases and the surface becomes irregular enough to promote friction. Applying oil on the door hinges can reduce the amount of friction and thus it will decrease it.

Friction should always be avoided.

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
The given statement is false.
Friction is a necessary evil because without friction we will not be able to set our bodies in motion or stop the bodies which are in motion. Friction is absolutely necessary in our day to day activities. For eg it is the friction on the ground that helps us to walk and without friction it would not have veen possible to write on a paper.
Hence friction is important and cannot be avoided.

Friction is a force that oppose motion.

physics friction advantages and disadvantages of friction merits and demerits of friction and methods to reduce it friction: a necessary evil

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

The given statement is true.

Friction always acts in opposite direction to movement i.e it opposes the motion of an object. Air resistance is a frictional force which opposes motion through air.