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Please help me calculate velocity.

Posted: Sat Oct 09, 2010 6:11 am
by searchme
1. The problem statement, all variables and given/known data

1. Consider a man throwing a baseball. Given the following, calculate the velocity of the ball as it leaves his hand:
1. The distance from his shoulder socket (humeral head) to the ball is 70 cm.
2. The distance from his humeral head to the points of insertion of the muscles moving his arm forward is 9 cm (this is a simplification, as the shoulder is a complex joint).
3. The velocity of the muscle shortening is 2.6 m/sec..

Show your calculations neatly in the space provided to receive credit for your answer.
Express your answer in m /sec., and round your answer to the nearest tenth.


2. Relevant equations

Velocity = Distance / Time ????

3. The attempt at a solution

Here is my first attempt at this problem: 2.6 m/ sec = 260 cm/ sec.

70 - 9 = 61 cm

61 cm / 260 cm per second = 0.23 m /second?

Can anybody help me on how I should start this question? I would like to know how to start so I can begin to wrap my brain at it. Thank you. P.S. I don't know really know anything about velocity other than what I wrote above. Thank you!

Posted: Sat Oct 09, 2010 7:55 am
by JackBean
how can you get cm/[cm/s] = m/s? :roll:

Do you really think this is physiological question?

Posted: Sat Oct 09, 2010 2:29 pm
by Darby
Is this assuming the ball describes a simple arc centered on the shoulder? That's not how a ball is thrown, there are a bunch of levers moving at different speeds - just watch a video and try to figure out how much comes from the shoulder, the elbow, the twist of the forearm, the wrist, and the fingers.

Re: Please help me calculate velocity.

Posted: Sat Oct 09, 2010 6:06 pm
by searchme
Yes- I know. Lets use simple arch centered on the shoulder. Any thoughts on how I should calculate the velocity?