Two identical tuning forks, each of frequency 340Hz, are struck near a listener. One fork is then moved directly towards the listener with a constant speed u while the other remains stationary. If the listener hears 4 beats per second, calculate u. (Speed of sound in air =340ms−1.)
a) 2.0ms−1
b) 4.0ms−1
c) 3.8ms−1
d) 8.0ms−1