Solving a Physics Question: Wheel Mass 15kg, Radius 1m, Step 0.4m

[lionely]

I have no idea how to attempt this question, please help me. Anyone.

The question : The diagram shows a wheel whose mass is 15kg and radius 1m being pulled by a horizontal force F against a step 0.4m high. What inital force is just sufficient to turn the wheel so that it will rise over the step? What happens to the size of this horizontal force as the wheel rises?

This question is the last part of a long question, I did all the other parts. Can someone just break this down?

 

[Spinnor]

Does this get you started, did I make any mistakes?

 

[lionely]

Omg I knew IT! I should of made a triangle my father was trying to help me but he didn't listen!

 

[lionely]

I thank you so much, the .8m will be multiplied by the 150N