arlammers67

06-25-2008, 02:12 AM

Friction force equals the coefficient of friction times the normal force.

By calculating the ratio of shear forces to normal forces, one may calculate

the "required coefficient of friction," which is the coefficient of friction

needed to avoid slipping. From what I've read, on a flat surface, shear

force is the vector sum of anteroposterior and mediolateral ground reaction

force components, and normal is the vertical component. If the substrate is

cylindrical (as in the arboreal trackways that I use), then mediolateral and

vertical components each contribute some to shear and normal forces,

depending on where the limb contacts the cylinder. The anteroposterior

force component contributes only to shear. My question is: does pure torque

also contribute to the calculation of shear force? For example, if a person

steps onto the very center of a force plate and twists to the right, is the

shear force the vector sum of anteroposterior force, mediolateral force, and

the torque within the horizontal plane that does not result from

anteroposterior and mediolateral forces applied off-center? If it's an

arboreal substrate (which is my real question), does a torque around the

long axis of the branch trackway contribute to shear force? My guess is

that the "pure" torque (that torque which results from the limb exerting a

twisting moment, and NOT the torque that results from substrate reaction

forces being applied off-center to the cylinder) SHOULD be included in the

vector sum of shear components of vertical and mediolateral forces and the

anteroposterior force. Please e-mail me with your arguments or suggestions!

Thanks - Andrew Lammers, Dept of Health Sciences, Cleveland State

University, a.Lammers13@csuohio.edu.

By calculating the ratio of shear forces to normal forces, one may calculate

the "required coefficient of friction," which is the coefficient of friction

needed to avoid slipping. From what I've read, on a flat surface, shear

force is the vector sum of anteroposterior and mediolateral ground reaction

force components, and normal is the vertical component. If the substrate is

cylindrical (as in the arboreal trackways that I use), then mediolateral and

vertical components each contribute some to shear and normal forces,

depending on where the limb contacts the cylinder. The anteroposterior

force component contributes only to shear. My question is: does pure torque

also contribute to the calculation of shear force? For example, if a person

steps onto the very center of a force plate and twists to the right, is the

shear force the vector sum of anteroposterior force, mediolateral force, and

the torque within the horizontal plane that does not result from

anteroposterior and mediolateral forces applied off-center? If it's an

arboreal substrate (which is my real question), does a torque around the

long axis of the branch trackway contribute to shear force? My guess is

that the "pure" torque (that torque which results from the limb exerting a

twisting moment, and NOT the torque that results from substrate reaction

forces being applied off-center to the cylinder) SHOULD be included in the

vector sum of shear components of vertical and mediolateral forces and the

anteroposterior force. Please e-mail me with your arguments or suggestions!

Thanks - Andrew Lammers, Dept of Health Sciences, Cleveland State

University, a.Lammers13@csuohio.edu.