A rocket is traveling straight up from its launch pad. An observer 5.00 km from
the launch pad notices that at one instant, she must tilt her telescope 45.0
degrees upward to see the rocket. 10.0 seconds later, she must tilt her telescope
upward 50.0 degrees to see the rocket. What was the average speed of the
rocket?

Question

A rocket is traveling straight up from its launch pad. An observer 5.00 km from
 the launch pad notices that at one instant, she must tilt her telescope 45.0
 degrees upward to see the rocket. 10.0 seconds later, she must tilt her telescope
 upward 50.0 degrees to see the rocket. What was the average speed of the
 rocket?

anonymous · Answer

The average speed is the distance something travels divided by the time it takes to travel the distance.  You know the time, you need to find how far the rocket traveled.  

Change in distance =  $$\Delta y = y_f - y_i$$

So you need to find the position of the rocket when she begins observing the rocket and when she adjusts her telescope.  Use geometry.