FL5 C/P #3

Post Reply
NS_Tutor_Will
Posts: 685
Joined: Fri May 25, 2018 9:15 am

FL5 C/P #3

Post by NS_Tutor_Will » Wed Nov 07, 2018 8:50 am

A student asks,
If the question is only asking about the energy of the lower extremities why do you multiply the effeciency of the upper extremities as well?
With this question, the initial energy is actually generated in the lower extremities and then passed, in a series of steps, up through the body and eventually into the baseball. In other words, in order for the baseball to get its kinetic energy, the pitcher must begin generating that energy in the lower extremities and then "move it" up the body, to the arm, and eventually into the baseball. Thus, the efficiency at each step must be taken into account. Since the legs aren't really throwing the baseball (just directing energy into the arm, so to speak), we need to include the efficiency of the upper extremities, too.

I hope this helps!
mist.illusionist
Posts: 17
Joined: Mon Jan 28, 2019 9:21 am

Re: FL5 C/P #3

Post by mist.illusionist » Mon Mar 11, 2019 3:57 pm

Can you please explain why you have to divide KE by efficiency to get energy the lower extremities generated?
NS_Tutor_Will
Posts: 685
Joined: Fri May 25, 2018 9:15 am

Re: FL5 C/P #3

Post by NS_Tutor_Will » Tue Mar 12, 2019 8:22 am

We're basically trying to "undo" the process that led to the KE in the first place. Since that involved starting at the first step and then multiplying by efficiency in a series of steps, to get back to the initial energy, we have to divide in reverse order by those same efficiencies.

Here's what we did to find KE:

Initial energy * efficiency 1 * efficiency 2 * efficiency 3 * efficiency 4 = KE

So to get back to initial energy:

KE / efficiency 4 / efficiency 3 / efficiency 2 / efficiency 1 = Initial energy

Good luck!
Post Reply