A person of mass m is standing in an elevator of mass M. The elevator is moving downward, but has an upward acceleration of a. To an observer fixed on the Earth, the force exerted on the person by the floor of the elevator is
a. (m+M)g b. m(g+a) c. m(g-a) d. M(a-g) e. M(a+g)
I think I have the Free Body Diagrams correct, but im confused by finding the normal force on the person by the floor of the elevator.
Any help would be great. Thank you.