Question

Sprint 7:18 PM a kudu.com Kudu 2 Support A doppler fetal monitor is a hand-held ultrasound device that is used to detect a fetal heartbeat in prenatal care. The device works by measuring the speed of the fetus's ventricular wall and thereby tracking its heartrate Part a Suppose the fetus's ventricular wall moves back and forth in a pattern approximating simple harmonic motion with an amplitude of 1.7 mm and a frequency of 3.0 Hz. Find the maximum speed of the heart wall (in m/s) during this motion. Be careful of units! 0.032m/sAnower 1 of 4 attempts used CHECK ANSWER Scroll to 个@ Top Questions Contents Back

Answer 1

Part - (a) V_max = Aw = A(2 pi f) = 1.7 times 10^-3 times 2 times 3.14 times 3 V_max = 0.032 m/s Part - (b) Given f_0 = 2MH_z = 2 times 10^6 Hz V = 1500 m/s maximum frequency is observed when wall is moving towards the source f_max = (V + V_w/V) f_0 f_max = (1 + Vw/V)f_0 therefore V-w = 0.032 m/s f_max = f_0 + V_w f_0/V f_max - f_0 = V_w/V f_0 delta f = 0.032/1500 times 2 times 10^6 change in frequency delta f = 42.6 Hz part - (c) In this case device become observer and heart wall behave as source. Frequency observed f^' = (V/V - V_)w) f_max = (v/V - V_w) (v + V_w/V)f_0 f^' = (v + v_w/V - V_w) f_0 f^' = (1500 + 0.032/1500-0.032) times 2000000 f^' = 2000085.33 Hz shift delta f = f^' - f_0 delta f = 85.33 Hz