Unit 6

So here's green dude chillin in an elevator, going up to the 45th floor to see his purple lady friend. So he's now wizzing past in the elevator and at this very moment just passed the 10th floor. Because its pretty early in the morning there, there isn't much elevator traffic, so the elevator goes straight from floor 1 to floor 45. So while green dude is in the elevator passing the 10th floor, the elevator is moving at a constant velocity which means the two forces drawn below are balanced. This is why green dude doesn't even feel like he is moving (up or down).

So actually, before he even started his journey up the elevator shaft, green dude had to walk into the elevator when it was completely still. This means, the elevator had to accelerate in the very beginning in order to get to the constant speed above. So in the very beginning, the elevator accelerated and this caused the forces of N (normal force) and mg (mass*gravity, or weight) to become unbalanced. This means that green dude would have felt heavier, as the elevator accelerated upwards, even though his mass did not change. 

Green dude visits the lady friend, and eventually has to ride the elevator back down. So this means the elevator and himself, are both accelerating downwards. The acceleration once again causes an imbalance in the forces, causing the green dude to feel a lot lighter!