Answer
The fastest speed that the car can go over the hill without losing contact with the ground is $23.2~m/s$
Work Step by Step
To find the maximum speed, we can assume that the normal force is zero, and the gravitational force provides the centripetal force to keep the car moving in a circular path. Then the radial acceleration is $g$:
$\frac{v^2}{r} = g$
$v = \sqrt{g~r}$
$v = \sqrt{(9.80~m/s^2)(55.0~m)}$
$v = 23.2~m/s$
The fastest speed that the car can go over the hill without losing contact with the ground is $23.2~m/s$.
