Givens: (Write down what you know)

m=0.21kg

v=3.5m/s

r=0.50m

What am I looking for? F_{c} on the shoe at the moment of my givens

Do I have a formula that relates the givens to what I want?

F_{c}=mv^{2}/r

Plug in

F_{c}=(0.21)(3.5)^{2}/0.50

In cases where you don't have a single formula that has everything you want, do you have a formula using some or all of your givens that gives you something that is useful?