Answer:
(a) The horizontal ground reaction force

(b) The vertical ground reaction force

(c) The resultant ground reaction force

Explanation:
Given
John mass , m = 65 kg
Horizontal acceleration ,

Vertical acceleration ,

(a) Using Newton's 2nd law in horizontal direction

=>

Thus the horizontal ground reaction force

(b) Using Newton's 2nd law in vertical direction

=>

=>

Thus the vertical ground reaction force

(c) Resultant ground reaction force is

=>

=>

Thus the resultant ground reaction force
