If I stand up on an accelerating bus, static friction between my shoes and the bus will do work. - I suppose it is negative work on the bus, and when velocity is constant it does no work at all, am I right? - does it do any work on me? - if I do not stand on my feet , but sit leaning my back onto a chair, the bus is pushing me. It is doing positive work on me, what about friction? is it zero? -if it is zero, why? the result is different, me moving at same speed of the bus, why is work done different? Thanks.