Inertia is the correct answer!
law of electromagnetic induction hope this helps
Answer:
The free body diagram of John is shown in the attached figure (in the FBD john's mass is supposed to be concentrated at his center of mass and FBD is made of center of mass)
b) As shown in the FBD the ground reaction forces are:
i) In X direction 
ii) In Y direction 
c) The respective accelerations in x and y direction's is calculated by newton's second law as indicated under

Because the scientific method can go around in a circle as many times as neccisary to get the results you need