A few simple physics questions on motion, vectors, projectile motion

!. At what angle (from the horizontal) should I shoot a cannon at to theoretically maximize distance traveled
----The correct answer is 45 degrees. explain why.

2. Find the average velocity of a race car driver who took 48 seconds to drive once around an oval track 1600 meters around
-----the correct answer is 0m/s. explain why.

3. At what angle (from the horizontal) should I shoot a cannon at to theoretically maximize my time in the air?
----the correct answer is 90 degrees. explain why.

If possible explain it in very simple terms. Thanks!

1. See 2nd answer in the link.

2. Displacement = difference between initial and final positions. This is zero for exactly 1 circuit.
Average velocity = displacement/time = 0/48 =0
You have to remember that displacement is not the same as distance travelled, as displacement is a vector. And velocity is not the same as speed, as velocity is a vector.

3. The time in the air is controlled by the vertical component of velocity. The bigger this is, the longer it stays in the air. The vertical component = v.sin(theta); the maximum this can be is when sin(theta) =1, i.e when theta = 90degrees.