Please answer, this is a quiz

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

The rocket is fired vertically and tracked by the radar station shown. when θ reaches 66°, other corresponding measurements give the values r = 32700 ft, r¨ = 85 ft/sec2, and θ˙ = 0.019 rad/sec. calculate the magnitudes of the velocity and acceleration of the rocket at this position.

Explain why electric current cannot exist if a current doesn't have a voltage source.