Two Biomedical physics questions involving equilibrium.

[ardy121]

Homework Statement

1) A person of weight 600N has her feet horizontal but her heels are slightly off the ground so that her weight is supported by the reaction force from the floor on each foot. Two other forces are assumed to be acting on the foot : a reaction force from the tibia on the foot and the force due to the Achilles tendon. The persons weight is assumed to be evenly distributed on the two feet. Find the magnitudes of the forces acting on the foot.

Distance between reaction force and achilles = 25cm
Distance between reaction force and lower leg bones =18cm

2)A 700N, 1.7m tall person rests horizontally on two scales. Assuming the center of mass of the person is at a distance 96cm from the feet and that the distance between the scales is 1.6m, find the reading on each scales.

These are practice for an exam i have tomorrow, and i can't do these two questions at all :/

Thanks HEAPS!

Homework Equations

Torque = force x sin (theta) x distance

The Attempt at a Solution

I have no idea to begin with 1) and for 2) find the torques?
If someone just does the answer ill be able to work it out! :)

 

[tiny-tim]

hi ardy121!

(have a theta: θ )

these are https://www.physicsforums.com/library.php?do=view_item&itemid=64" problems

1) there are three forces on the foot: the normal force from the ground, which you are told is 300N, a force downward through the tibia, and a force (of tension) upward through the tendon

draw those three forces on the diagram, and get both the forces and the moments about some suitable point (the torques) to add to zero

2) take moments (torques) about the centre of mass