The first and most important step in solving a projectile motion problem is to split the givens into x and y components. 

X components	Y components
a= 0	a=-9.8m/s^2
v= constant	v= changing
d=range	d=height
t= same for both values

knowing that the time elapsed on both axes are the same, we can incorporate the big 5 equations to find the time for whichever axis is possible.
for x:   dx= (vx)(tx)
for y:   Δdy= vy Δt + ½ ayΔt²


Now this value can be used along with other available values to solve for any missing values.

The Physics Behind Rollercoasters

            Something most people do not realize is that rollercoasters do not have an engine. After the car has been pulled to the top of the first drop by a mechanical belt, the rest of the ride is completed through the conversion of potential energy (stored energy) to kinetic energy (motion energy). This is why as hills shorten and the angle of curves become more shallow as the ride progresses.
             When you descend that first hill, different types of wheels keep the ride interesting and safe. Running wheels guide the coaster on the track, friction wheels control lateral motion, etc. The compressed air brakes stop the car as the ride ends.

              As for my favorite rollercoasters, I would say they are The Behemoth and The Mighty Canadian Minebuster, both at Canada's Wonderland. Behemoth, with a 230 feet drop and reaching speeds of 125 km/h is definitely the favorite of many. The Minebuster however only reaches speeds of 90km/h, but the old wooden design and rickety tracks make it one of my favorites.