Tag: physics

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Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas at constant volume is 5.0 ${ JK }^{ -1 }{ mol }^{ -1 }$. If the speed of sound in this gas at NTP is 952${ ms }^{ -1 }$, then the heat capacity at constant pressure is (Take gas constant R=8.3${ JK }^{ -1 }{ mol }^{ -1 }$)

  1. $8.5{ JK }^{ -1 }{ mol }^{ -1 }$

  2. $8.0{ JK }^{ -1 }{ mol }^{ -1 }$

  3. $7.5{ JK }^{ -1 }{ mol }^{ -1 }$

  4. $7.0{ JK }^{ -1 }{ mol }^{ -1 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

When an ideal diatomic gas is heated at a constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is

  1. $\dfrac {2}{5}$

  2. $\dfrac {3}{5}$

  3. $\dfrac {3}{7}$

  4. $\dfrac {5}{7}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Th\quad fraction\quad is\quad \frac { \triangle V }{ \triangle Q } \quad =\quad \frac { { _{ n }{ C } _{ v } }\triangle T }{ { _{ n }{ C } _{ p } }\triangle T } \ \frac { \triangle V }{ \triangle Q } =\frac { { C } _{ V } }{ { C } _{ P } } \quad =\quad \frac { 1 }{ Y } \ as\quad we\quad know\quad y\quad =\quad { C } _{ P }/{ C } _{ V }\ y\quad for\quad diatomatic\quad gas\quad :\quad \ { C } _{ P }\quad of\quad diatometic\quad gas\quad :\quad \frac { 7 }{ 2 } \ { C } _{ V }\quad of\quad diatometic\quad gas\quad :\quad \frac { 5 }{ 2 } \ y\quad =\quad \frac { { C } _{ P } }{ { C } _{ V } } =\frac { 7/2 }{ 5/2 } =\frac { 7 }{ 5 } \ \frac { \triangle V }{ \triangle Q } =\frac { 1 }{ y } =\frac { 1 }{ 7/5 } =\frac { 5 }{ 7 } \quad (D)$

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

For an ideal gas, the heat capacity at constant pressure is larger than that at constant volume because

  1. positive work is done during expansion of the gas by the external pressure

  2. positive work is done during expansion by the gas against external pressure

  3. positive work is done during expansion by the gas against intermolecular forces of attraction

  4. more collisions occur per unit time when volume is kept constant
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When  heat  is  supplied  at  constant  volume,  temperature  increases accordingly  to  the  ideal  gas  equation.

$P=\dfrac { nRT }{ V } $

as  V  is  constant  and  T  is  increasing,  pressure  will  also  increase.

Than at constant pressure  as temperature is increase volume increases, resulting in expansion of the gas, resulting in positive work, Hence the heat given is used up for expansion and then to increases the internal energy . The heat capacity at constant pressure is larger.

Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

A transverse wave on a string has an amplitude of $02m$ and a frequency of $175Hz$. Consider a particle of the string at $x=0$. It begins with a displacement $y=0$ at $t=0$, according to equation $y=0.2\sin{(kx+\omega t)}$. How much time passes between the first two instant when this particle has a displacement of $y=0.1m$>

  1. $1.9ms$

  2. $3.9ms$

  3. $2.4ms$

  4. $0.5ms$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

For a string clamped at both its ends, which of the following wave equation is/are valid for a stationary wave set up in it? (Origin is at one end of string).

  1. $y=A\sin kx.\sin \omega t$

  2. $y=A\cos kx \sin \omega t$

  3. $y=A\sin kx. \cos \omega t$

  4. $y=A\cos kx \cos \omega t$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

For all values of t, y$=0$ at $x=0$
Hence, (A) and (C) are correct.

Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

A certain strings will resonate to several frequencies , the lowest of which is $200$cps.what are the next three higher frequencies to which it resonates? 

  1. $400,600,800$

  2. $300,400,500$

  3. $100,150,200$

  4. $200,250,300$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Given,  The Lowest frequency is $200cps$

Let  $f$ resonant the fundamental frequency, then the next higher frequency is: $2f,3f,4f$

$2\times200=400cps,3\times200=600,4\times200=800cps$


Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency of $45 Hz$. The mass of the wire is $3.5 \times 10^{-2}kg$ and its linear mass density is $4.0 \times 10^{-2} kgm^{-1}$. What is the speed of a transverse wave on the wire?

  1. $69 \ ms^{-1}$

  2. $79 \ ms^{-1}$

  3. $89 \ ms^{-1}$

  4. $99 \ ms^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a wire vibrating in its fundamental mode, the frequency f = v / (2L). However, we can use the relation v = sqrt(T/mu). Given the mass M = 0.035 kg and linear density mu = 0.04 kg/m, the length L = M/mu = 0.875 m. The fundamental frequency f = v / (2L) = 45 Hz, so v = 45 * 2 * 0.875 = 78.75 m/s, which rounds to 79 m/s.

Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

A person observe two points on a string as a travelling wave passes them. The points are at $x _ { 1 } = 0$ and $x _2 = 1m$. The transverse motions of the two points are found to be as follows: $y _ { 1 } = 0.2 \sin 3 \pi t$
$y _ { 2 } = 0.2 \sin ( 3 \pi t + \pi/8 )$ What is the frequency in Hertz?

  1. $1.5 Hz$

  2. $3 Hz$

  3. $4.5 Hz$

  4. $1 Hz$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The transverse motion is given by y = A sin(omega * t + phi). Comparing y1 = 0.2 sin(3 * pi * t) with the standard form, omega = 3 * pi. Since omega = 2 * pi * f, we have 3 * pi = 2 * pi * f, which gives f = 1.5 Hz.