posted by Donnie .
(a) At a certain instant, a particle-like object is acted on by a force F=(2.9N)i-(1.7N)j+(5.7N)k while the object's velocity is v= -(3.2m/s)i+(4.5m/s)k. What is the instantaneous rate at which the force does work on the object? (b) At some other time, the velocity consists of only a y component. If the force is unchanged, and the instantaneous power is -6.0 W, what is the velocity of the object just then? (Give your answer without a unit vector.)