Work and power when lifting weights

[physicscholar]

something i can't grasp is
why is it that when you lift one end of a log and the center of mass is raised a certain height you are using less energy than lifting the whole log with the center of mass raised to the same height
does it have to do with the amount of mass you're raising?

 

[russ_watters]

Are you talking about the mechanical energy done on the log or the chemical energy used by your muscles? The mechanical energy is equal in the two cases.

I'm also unsure of how this relates to the title of the thread - you didn't ask anything about power.

 

[Rajini]

Hi
if i understand properly your question...i think you must understand the gravity and balancing methods..
For e.g.,
case 1. When you lift from one end->it means a 2nd order lever (load is the log or somewhere in log, fulcrum (fixed) at the other end and)..
case 2. When you lift by holding the log somewhere (not from end!)->it means a 3rd order lever (load is the log or somewhere in log, fulcrum (fixed) where you hold the log..
Obviously it will easier in 1.
Hope this helps.