Answer:
r = 22.78 m
Step-by-step explanation:
For this exercise let's use Newton's second law
Axis y
N- W = 0
N = W
X axis
F = m a
Where the acceleration is centripetal
a = v² / r
The force is the friction that the formula has
fr = μ N
fr = μ mg
Let's replace
μ m g = m v² / r
r = v² / μ g
Let's reduce the speed to the SI system
v = 45 km / h (1000 m / 1 km) (1h / 3600 s) = 12.5 m / s
r = 12.5 2 / (0.7 9.8)
r = 22.78 m