Consider applying Newton's second law to a man riding an elevator (perhaps to calculate his acceleration).

Which of the following forces must be considered? Choose all that apply.

1. The force that the man's head exerts on his neck.
2. The force of gravity on the elevator.
3. The force the elevator cable exerts on the elevator car.
4. The force that the elevator floor exerts on the man's feet.
5. The force that the man's feet exert on the floor of the elevator.
6. The force of gravity on the man.