Hi there!
Since the car is not accelerating in the vertical direction, the only net force acting on the car is in the horizontal direction.
This is the force due to friction, which is also providing the centripetal force. So:
[tex]\Sigma F_x = F_f[/tex]
[tex]\frac{mv^2}{r} = F_f\\\\[/tex]
m = mass (kg)
v = velocity (m/s)
r = radius (m)
Plug in the given values:
[tex]F_f = \frac{1500(15^2)}{50} = \boxed{6750 N}[/tex]
