A rock with a mass of 2.80 kg is moving with velocity (5.20î − 1.20ĵ) m/s. (HINT: v2 = v · v.)

(a) What is the rock's kinetic energy (in J) at this velocity?

_________J

(b) Find the net work (in J) on the rock if its velocity changes to (8.00î + 4.00ĵ) m/s.

_________ J