By holding a bike wheel (mass m, radius r, so that it rotates freely about its...

By holding a bike wheel (mass m, radius r, so that it rotates freely about its vertical center axis) and standing on a circular platform (a disk of mass M and radius R, free to rotate about its vertical center axis), describe a method to measure your mass using a stopwatch (an interesting balance!). Explain your method using physics equations and manipulations to prove that your method will work

Expert Solution

It's a question similar with the gyroscope movement."The total angular momentum of a system remains constant if the net external torque acting on the system is zero."

This system: {the experimeter+wheel, the platform}

Keep the wheel on its axis and give a spin to it to start to rotate. Position it in such a way to rotate horizontally. Then, 'flip' (tilt) the wheel 180 deg (apply a torque to it). The platform will strat to rotate.

The change of the angular momentum of the wheel (the direction of the angular momentum reverses) is compensated for by your own change in angular momentum.

r, R = radii of the wheel

For the platform+human,

Angular speed () can be calculated using the stopwatch.

see this video: http://www.arborsci.com/deluxe-bicycle-wheel

genius_generous answered 1 hour ago

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