# Homework Help: Need Help Magnitude and Forces problem

1. Sep 9, 2008

### sfs007

Need Help ASAP!! Magnitude and Forces problem

1. The problem statement, all variables and given/known data

Based on a free body diagram of a runner running around a turn on a track:

1. An estimate of the lean you would have while running at your maximum speed on a university track and
2. estimates of the relative distances between your mass center and the various forces depicted in the free body diagram, and
3. an estimate of the magnitudes of the forces depicted in the free body diagrams,

You should:
Calculate the magnitudes and directions of the moments produced about the mass center by each of the forces shown in the free body diagram. The moment magnitudes should be given with appropriate units or dimensions.

Weight is 150lbs or 68kg
Height is 5'8

Last edited: Sep 9, 2008
2. Sep 9, 2008

### LowlyPion

Re: Need Help ASAP!! Magnitude and Forces problem

Welcome to PF.

What would be your attempt at a solution?

3. Sep 9, 2008

### sfs007

Re: Need Help ASAP!! Magnitude and Forces problem

I dont know where to start. Im in grad school for Health promotion and this is a biomechanics class which I know nothing about

4. Sep 9, 2008

### LowlyPion

Re: Need Help ASAP!! Magnitude and Forces problem

What is the radius of the track?

When you are traveling around a curve what is the radial force? MV2R.
http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html#cf

What weight shift do you need to compensate for that? That would be the centrepital force you need to balance. You balance that with your weight shifted how far? Draw a diagram and figure how to balance with the foot as a pivot. Weight down times shift must be Centripetal force times the height of the Center of mass away from the foot.

5. Sep 9, 2008

### sfs007

Re: Need Help ASAP!! Magnitude and Forces problem

still lost me!

6. Sep 9, 2008

### LowlyPion

Re: Need Help ASAP!! Magnitude and Forces problem

Sorry, I can't do the problem for you.

Look at the equations.

Make a drawing of the forces involved, the runner overhead to figure the mv2/R and then head on and identify the side force you just calculated and how shifting the weight from over the center of mass can offset it.
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