Energy Conservation

When we had only linear KE or translational KE of

KE = ( 1/2 ) m v2

we found Energy Conservation to be very useful, writing

Ei = Ef

where E is the total energy,

E = KE + PE

the sum of the Kinetic Energy and the Potential Energy.

Now we have an additional form of Kinetic Energy, KErot. Now the total energy must include that as well,

E = KErot + KEtrns + PE

Energy is still conserved, so when we write

Ei = Ef

we are really writing

KErot,i + KEtrns,i + PEi = KErot,f + KEtrns,f + PEf

where we have now written KEtrns to explicitly state "translational KE" or

KEtrns = ( 1/2 ) m v2

As before, energy changes from one form to another but the total energy remains constant.

Rotational KE

Return to ToC, Rotational Kinematics
(c) 2005, Doug Davis; all rights reserved