Answer this Question on Newton's Laws

Question

Why it is relatively easy to walk down the aisle on an airplane in flight, but would be difficult to do during takeoff or landing when using Newton's laws?

Answer 1

William's answer is correct, I just want to elaborate.

In flight, you are moving with the plane at the same speed as the plane. Relative to the plane, you are standing still. Walking down the aisle is no different than when the plane is on the ground and not moving.

During landing and take-off, the plane is accelerting or decellerating. It exerts a force on you to try and keep you up with that motion. If you're standing in the aisle, the only force the plane can use to move you is the friction force at your feet. That force will cause you to tip forward or backward because it is not acting through your center of gravity. If you try to walk down the aisle you're in trouble keeping your balance.

Answer 2

When the airplane is in steady-state flight, the velocity is approximately constant therefore there is no acceleration. If there is no acceleration, then Newton's 2nd Law, F = ma, tells us there is no force from that acceleration so you feel like you are just walking along the street.

If you are in takeoff or landing, the velocity is either increasing or decreasing rapidly meaning you are experiencing an acceleration (either positive or negative). Newton's 2nd Law tells us that there will be a force associated with that acceleration and that force will make it hard to keep your balance as you walk down the aisle.