2019-03-01_Physics_Times

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   [2010]

   
   


8. 
   

[2014]

[2013]

[2011]

[2010]

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[2011]1]

[2010]

7. [2010]

A whistle emitting a loud sound of frequency 540
Hz is whirled in a horizontal circle of radius 2 m and
at a constant angular speed of 15 rad/s. The speed
of sound is 330 m/s. The ratio of the highest to the
lowest frequency heard by a listener standing at
rest at a large distance from the center of the circle
is
(a) 1.0 (b) 1.1 (c) 1.2 (d) 1.4
An engine moving away from a vertical cliffblows a
horn at a frequency f.Its speed is 0.5% of the speed
of sound in air .The frequency of the reflected sound
recieved at the engine is
(a) 0.990 f (b) 0.995f (c) 1.005f (d) 1.010f

A speaker emits a sound wave of frequency f 0.
When it moves towards a stationary observer with
speed u, the observer measures a frequency f 1. If
the speaker is stationary, and the observer moves
towards it with speed u, the measured frequency is
f 2. Then
(a) f f f 1   2 0 (b) f f 1  2
(c) f f 1  2 (d) f f f 1   2 0
A bus driving along at 39.6 kmph is approaching a
person who is standing at the bus stop, while
honking repeatedly at an interval of 30 seconds. If
the speed of the sound is 330 m/s, at what interval
will the person hear the horn?
(a) 31 seconds (b) 29 seconds
(c) 30 seconds
(d) The interval will depend on the distance of
the bus from the passenger
Velocity of sound measured at a given temperature
in oxygen and hydrogen is in the ratio
(a) 1 : 4 (b) 4 : 1 (c) 1 : 1 (d) 32 : 1

Thermodynamics

1. c 2. a 3. d 4. a 5. a

6. a 7. Delete8. b 9. a 10. b


7. d 12. b 13. c 14. d 15. c


8. a 17. b 18. d 19. c 20. c

Heat Transfer

1. b 2. d 3. d 4. a 5. c


2. a 7. b 8. a

Waves on String

1. d

Sound Waves

1. b 2. d 3. c 4. a 5. b


2. b 7. a

Thermodynamics

1.Sol: Along path - 1

Volume increases temperature also increases

Thermodynamics

1. 2. 3. 4. 5.

Heat Transfer

Waves on String

1.

Sound Waves

1. 2. 3. 4. 5.

6. 7.

V

T

constant (isobaric)

So internal energy increases

Heat is absorbed by the gas in path - 1

  Q nC T 1 P   T  ve

W W 2  1.

The possible correct option is (c).

2.Sol: Given that

5 5

2 2

U PV C nRT C   

5

2 2

nfR

    U nR T T

f 5, 7 / 5

(^) PV7/5constantP V5 7constant
3.Sol: For closed container W 0
   Q U W
     Q U nC TV
 
5 5
2 2
n R T  nR T
 
(^55) 10 10 (^35250)
2 2
    V P  Pa J
4.Sol: Change in internal energy is zero in any cyclic
process
 U 0
W  ve (Anticlock wise)
   Q U W
   Q  ve
5.Sol: In sudden expansion gas does not get enough
time for exchange of heat with the surrounding.
 Q 0
 So the process is adiabatic.
6.Sol: The given graph is
Thermodynamics
1.Sol:
2.Sol:
3.Sol:
4.Sol:
5.Sol:
6.Sol: