5.2 Mechanical Energy | General Physics 

i got 200,000J as well

HE said 200k but he probably wrote down 400k on accident bc he's doing this on the fly

Hey Jody, in reality when there is friction the energy transfer is not 'perfect' because energy is lost as thermal and sound energy. You would definitely be asked to calculate these in more advanced courses but for the sake of general physics we usually assume energy dissipated by friction is negligible.