A carriage begins to descend from the hump, which is 40 m high and 400 m long. Determine the speed

A carriage begins to descend from the hump, which is 40 m high and 400 m long. Determine the speed of the car at the end of the hump if the coefficient of resistance to movement of the car is 0.05.

h = 40 m.
S = 400 m.
g = 9.8 m / s ^ 2.
μ = 0.05.
V -?
Let’s write the law of conservation of energy: m * g * h = m * V ^ 2/2 + A.
The potential energy of the body is converted into kinetic energy and is spent on the work of the friction force.
The work of the friction force A is determined by the formula: A = Ftr * S.
The friction force Ffr is determined by the formula: Ffr = μ * N, where μ is the friction coefficient, N is the support reaction force.
The support reaction force N is determined by the formula: N = m * g * cosα, where ∠α is the angle of inclination of the plane.
cosα = √ (S ^ 2 – h ^ 2) / S.
cosα = √ ((400m) ^ 2 – (40m) ^ 2) / 400m = 0.99
A = μ * m * g * cosα * S.
m * g * h = m * V ^ 2/2 + μ * m * g * cosα * S.
g * h = V ^ 2/2 + μ * g * cosα * S.
V = √2 * (g * h – μ * g * cosα * S).
V = √2 * (9.8 m / s ^ 2 * 40 m – 0.05 * 9.8 m / s ^ 2 * 0.99 * 400 m) = 19.9 m / s.
Answer: the speed of the car at the end of the hill is V = 19.9 m / s.