1
JEE Main 2020 (Online) 5th September Evening Slot
+4
-1
Out of Syllabus
A driver in a car, approaching a vertical wall notices that the frequency of his car horn, has changed from 440 Hz to 480 Hz, when it gets reflected from the wall. If the speed of sound in air is 345 m/s, then the speed of the car is :
A
36 km/hr
B
54 km/hr
C
24 km/hr
D
18 km/hr
2
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
Assume that the displacement(s) of air is proportional to the pressure difference ($$\Delta$$p) created by a sound wave. Displacement (s) further depends on the speed of sound (v), density of air ($$\rho$$) and the frequency (f). If $$\Delta$$p ~ 10 Pa, v ~ 300 m/s, $$\rho$$ ~ 1 kg/m3 and f ~ 1000 Hz, then s will be of the order of (take the multiplicative constant to be 1) :
A
1 mm
B
$${3 \over {100}}$$ mm
C
10 mm
D
$${1 \over {10}}$$ mm
3
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
In a resonance tube experiment when the tube is filled with water up to a height of 17.0 cm from bottom, it resonates with a given tuning fork. When the water level is raised the next resonance with the same tuning fork occurs at a height of 24.5 cm. If the velocity of sound in air is 330 m/s, the tuning fork frequency is :
A
2200 Hz
B
3300 Hz
C
1100 Hz
D
550 Hz
4
JEE Main 2020 (Online) 4th September Evening Slot
+4
-1
Out of Syllabus
The driver of a bus approaching a big wall notices that the frequency of his bus's horn changes from 420 Hz to 490 Hz when he hears it after it gets reflected from the wall. Find the speed of the bus if speed of the sound is 330 ms–1.
A
91 kmh–1
B
81 kmh–1
C
61 kmh–1
D
71 kmh–1
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