# Bio-mechanics Help! (Centripetal and Tangential acceleration)

1. Oct 8, 2011

### wit13

this is the question:

Pick joint of the human body. With reference to this joint and the concepts of tangential and centripetal acceleration, provide an example and explain:

A. an activity in which tangential acceleration is zero, centripetal is non-zero

B. an activity in which centripetal acceleration is zero, tangential is non-zero.

Any assistance would be greatly appreciated.

2. Oct 9, 2011

### 256bits

You do know what tangential and centripital acceleration are, or is that where you are stumped.

I would try to pick an activity or joint, and try to determine the forces their direction acting on that joint. Are the forces predominantly along the bones at the joint, or perpendicular to the joint causing a moment or twisting. There would have to b some movement of the joint. Just pushing on a wall may give a force on a joint but no acceleration.

Activities are:
running, jumping, weight lifting, horseback riding, throwing a ball, sitting, watching television, walking, picking a paperclip off the floor, playing on a swing, eating, race car driving, swimming, dancing, snapping your fingers, doing hula-hoop, typing on a keyboard, ...

joints: knuckles, wrists, elbow, shoulder( ball socket), neck, jaw, spine, hip, ....

Activity: running
Joint: knee, thigh, ankle
Acceleration at joint: centripital, tangential or both
Explain :

activity: weight lifting
Joint: shoulder, elbow
Accel : ??
Expalin:

Etc:

Last edited: Oct 9, 2011
3. Oct 9, 2011

### wit13

thanks for your help, I ended up digging up my physics book for a little refresher.

I was having trouble visualizing how the forces with work with respect to the joints

4. Oct 9, 2011

### 256bits

I think it is a tough problem, but say you want to build an artificial hand. You would need to know what forces are acting on the joints so it doesn't end up looking like that thing from "Hell Boy"