Subject :NSO Class : Class 8
An object vibrates 7200 times in 8 minutes. A girl standing close to the object hears
A 
B 
C 
DNo sound.
Ans 1:
Class : Class 8
The frequency is 900 hertz and can be heard by a human ear.
Ans 2: (Master Answer)
Class : Class 1
The correct answer is D.