Imagine you are a roller coaster designer, and are asked to mathematically represent the curve of the first
drop of a new ride.
By looking at some of your favorite coasters, you determine that the optimal slope for the ascent, when
the car is being pulled up the slope by a chain, is 0.7. The slope of the first drop that will be the most
thrilling (without being dangerous) is -1.5.
You decide to connect these two straight stretches, y = L, and y = L₂, with a parabola of the form
y = f(x) = ax + bx+c, where x and f(x) are measured in meters.
In order for the curve of the track to remain smooth, you must make sure that the linear segments, L, and
L₂, have the same slope at each endpoint of the parabola, points P and Q. This ensures that the parabola
is differentiable, as well as continuous at the endpoints. Choose point P, the left endpoint of your
parabola, as your origin, to simplify calculations.
a) Draw a rough sketch of L, with slope 0.7, ending at point P. Then sketch L, with slope -1.5,
starting at point Q a short distance to the right and below point P. Finally, sketch the parabola that
would connect P and Q while matching the slopes of L, and L₂.
b) If the horizontal distance between P and Q is 40 meters, write equations in a, b, and c that make
sure the track is smooth at the connections P and Q.
c) Solve the equations for a, b, and c to find the equation of the parabola that connects P and Q.
d) Using your calculator or a computer, plot the parabola f(x). Compare this to your original sketch in
part a) by noting any similarities or differences.
e)
How much higher is point P than point Q?
f) Find the maximum height of the coaster algebraically. Verify your answer by graphing f(x) on your
calculator.