If the bus is taking off (literally) at a 30 degree angle, at 75mph, then there will be a motion upwards (vertical) and a motion forwards (horizontal). These motions are independent of each other, which means you can split them up and work out how far the bus travels, upwards/downwards and forwards/backwards.

This is done using good old trigonometry.
So for the vertical motion the speed at which the bus is going upwards initially is:

The bus would decrease in speed upwards due to gravity, until it stops and then start falling, like throwing a ball upwards. How long would the bus take to rise and fall to the same level?

Final speed = initial speed + (acceleration x time)

1.675 seconds to reach the top of its flight.

How high has the bus gone, before it starts to comes down?