Physics help! center of mass

Question

Hello! Where would the center of mass be located if one were to raise one foot?

(e.g. above the hip, etc.) We used percentage height to calculate the center of mass so I'm not sure!

Answer 1

Hi Rin F.,

The exact answer is going to depend on the distribution of mass along the lifted leg, and also on how you bend the leg (bend at the knee, or at the hip, or both ....). You are likely to need some geometrical data on body parts. But you may be able to squeeze by by getting a helper and a spring scale. Lie supine, and balanced, in the desired position, on a narrow swing (i.e., balanced on a "knife-edge"). Then extend the bent leg fully, and use the spring scale to measure the downward force that leg generates. That will give you a torque, translating to a mass movement. Ratio that to your total body mass, and proportionate, etc., etc.

Remember, there are always ways to measure properties cheaply and ingeniously!

--Cheers, -- Mr. d.