Driving along a convex bridge, the radius of curvature of which is R = 128 m, the car at the top point presses

Driving along a convex bridge, the radius of curvature of which is R = 128 m, the car at the top point presses on the bridge with a force whose modulus is 20% less than the modulus of gravity acting on the car. determine the vehicle speed module.

R = 128 m.
P = 0.8 * Ft.
g = 9.8 m / s ^ 2.
V -?
Two forces act on the car at the top of the bridge: the force of gravity Ft directed vertically downward, and the reaction force of the bridge to the car N directed vertically upward.
Let’s write 2 Newton’s law: m * a = Fт – N.
N = Fт – m * a.
The force of gravity Ft is determined by the formula: Ft = m * g.
The centripetal acceleration a is determined by the formula: a = V ^ 2 / R.
According to Newton’s 3 law: with what force the bridge presses on the car N with the same modulus of force the car presses on the bridge R.
N = P.
P = Ft – m * a.
0.8 * m * g = m * g – m * V ^ 2 / R.
0.8 * g = g – V ^ 2 / R.
V ^ 2 / R = g – 0.8 * g.
V ^ 2 = 0.2 * g * R.
V = √0.2 * g * R.
V = √0.2 * 9.8 m / s ^ 2 * 128 m = 15.84 m / s.
Answer: vehicle speed V = 15.84 m / s.