A car is driven at constant speed over a circular hill and then into a circular valley with the same radius. At the top of the hill, the normal force on the driver from the car seat is 0. The driver's mass is 77.8 kg. What is the magnitude of the normal force on the driver from the seat when the car passes through the bottom of the valley?

therefore normal reaction on the driver from the seat when the car passes through the bottom of the valley = 1520.55 N

Explanation:

let speed be v

at top of hill

mg-N = mv^2/R (N=0 at the top of the hill)

==> mg=mv^2/R

at bottom

N-mg=mv^2/R

therefore,

N = 2mg = 2*77.8*9.81 = 1520.55 N

therefore normal reaction on the driver from the seat when the car passes through the bottom of the valley = 1520.55 N