When I was standing on the scales in my surgery today (I am a doctor), I noticed that the needle moved very slightly, exactly in time with my heartbeat. What could account for this fluctuation?
• Newton’s third law of motion states that for every action there is an equal and opposite reaction. With every heartbeat, the heart’s ventricles forcibly expel about 70 millilitres of blood into the pulmonary artery and the same volume into the aorta. The heart itself experiences a reaction in the opposite direction. Since the heart is well anchored in the chest, the entire body moves slightly. A sensitive scale can easily…
