In the opening scene from Star Wars: Episode IV – A New Hope (1977) we see a spaceship cross the screen and then an Imperial Destroyer follow.

We can ask the question what is the velocity of the Imperial Cruiser?

Solution: In order to determine a velocity we need a distance and a time.  From the internet we can find that the length of an Imperial Destroyer is 1600m. If we time the clip we see that it takes the Imperial Destroyer 20s to fully enter the screen. So its velocity is:

v = {\Delta x \over {\Delta t}} = {1600m \over{20s}} = 80 m/s.

Eighty meters a second is 288 km/hr or 179 mph. The spacecraft is moving faster than a car, but not as fast as a plane.