Rate of change of momentum for object following a kissing circle

[Nal101]

The "kissing circle"

Homework Statement

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?

Homework Equations

p = mv
$$\Delta$$p = F_net$$\Delta$$t
dp/dt = magnitude of V / R (sry don't know how to put that in latex)

The Attempt at a Solution

Question 1: Velocity divided by radius? Using the 3rd equation, but the units don't 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.