Here it goes: Expectant parents are thrilled to hear their unborn baby's heartbeat, revealed by an ultrasonic motion detector. Suppose the fetus's ventricular wall moves in simple harmonic motion with an amplitude 1.80 mm and a frequency of 115 per minute. (a) find the maximum linear speed of the heart wall. Suppose the motion detector in contact with the mother's abdomen produces sound at precisely 2MHz, which travels through tissue at 1.5 km/s (b) Find the maximum frequency at which the sound arrives at the wall of the baby's heart. (c) Find the maximum frequency at which reflected sound is received by the motion detector. So far i have realized that this would be a problem relating to the Doppler Effect. This is where i have started. However I dont no what is what. A = 1.8 mmm (What would I use that for?) F(baby) = 115 (Again, What or Where does this go?) F F(motion detector) = 2MHz (I am sure this goes in the Doppler Effect Formula) V (tissue) = 1.5 km/s What direction do I go to answer these questions? I am truly lost.