The "kissing circle"

Nal101

1. The problem statement, all variables and given/known data
An object moving at a constant speed of 31 m/s is making a turn with a radius of curvature of 4 m (this is the radius of the "kissing circle"). The object's momentum has a magnitude of 87 kg·m/s.
What is the magnitude of the rate of change of the momentum?
What is the magnitude of the net force?


2. Relevant equations
p = mv
[tex]\Delta[/tex]p = F_net[tex]\Delta[/tex]t
dp/dt = magnitude of V / R (sry dont know how to put that in latex)

3. The attempt at a solution
Question 1: Velocity divided by radius? Using the 3rd equation, but the units dont check out.
I am lost
Question 2: How do I find t, and afterwards, the answer would be F_net = 87 (change in momentum) * t (change in time)

rock.freak667

the rate of change of momentum is just acceleration so you need to find the centripetal acceleration.