Question

A motor cycle starts from rest and accelerates along a straight path at `2m//s^(2)`. At the starting point of the motor cycle there is a stationary electric siren. How far has the motor cycle gone when the driver hears the frequency of the siren at `94%` of its value when the motor cycle was at rest ? (Speed of sound = `330ms^(-2))`
A. 49 m
B. 98 m
C. 147 m
D. 196 m

Answer 1

Correct Answer - B
when source in stationary and observer is moving away from the source .
` n^(t) =n((V-V_(0))/(V))`
`implies 0.94 n=n((330-V_(0))/(330))`
` implies V_(0) =19.8 m//s`
`therefore V_(0)=0+2as`
` therefore S=(V_(0)^(2))/(2a)`
`=(19.8xx19.8)/(2xx2)`
=98 m.