Why do we hear a higher frequency apparently when we approach a stationary sounding railway engine?

Why do we group data?

Why do we call our heart myogenic ?

Why do we call our heart myogenic?

Why do we need pure substances ?

The ratio of the apparent frequencies of a car when approaching and receding a stationary observer is 11:9 What is the speed of the car, if the velocity of sound in air is 330 m/s?

A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed vms^(-1) . The velocity of sound in air is 300 ms^(-1) . If the person can hear frequencies upto a maximum of 10,000 Hz .The maximum value of v upto which he can hear whistle is

Why do we call density as a derived quantity?

Why do we need appendicular skeleton ?

Why do we add alum to purify water ?

A motorcycle starts from rest and accelerates along a straight line at 2.2(m)/(s^2) . The speed of sound is 330(m)/(s) . A siren at the starting point remains stationary. When the driver hears the frequency of the siren at 90% of when motorcycle is stationary, the distance travelled by the motorcyclist is