It is one of the important means of modern medical diagnosis. The doctor measures the time interval between two adjacent peaks on the electrocardiogram, that is, the cardiac cycle, that is, the heartbeat.
Solution: (1) From the heart rate γ A =60 beats/min, we can know that the cardiac cycle T a =1s.
That is, you need 1. Move the electrocardiogram by 25 mm.
Thus, the stretching movement speed V = 25mm/s can be obtained.
(2) According to B's electrocardiogram, it takes λ=20mm to move the drawing.
That is, B's cardiac cycle T B = 0.8s. 1 min and B's heartbeat times: γ=60s÷0.8s=75 times.