Please use examples like a person is walking on a moving a train. What happens to the velocity of the moving object if the frame reference does not have constant velocity?
In: Physics
Say you’re sitting on a bench. From your perspective a train is moving from left to right.
Say a person is walking on the train from right to left at a constant speed. But the train itself is slowing down. You’ll perceive this person as walking at a normal pace or a slightly fast pace.
Say instead the train is speeding up, you’ll perceive this person as walking at a slow pace.
Say instead the person is walking on the train from left to right at a constant speed. Now, regardless of whether the train is slowing down or speeding up, to u’ll perceive this person as walking at a fast pace. This is because they are going in the same direction as the train.
In all these cases the person is walking at a constant speed but the direction and the speed of the frame of reference, the train, determines your perspective.
Because that is how an inertial reference frame is defined. If a reference frame has a changing inertia, then it has a force being applied to it, and that force makes it different from a frame experiencing a different (or no) force.
If a reference frame has no force acting on it, then it is the same as any other frame having no force acting on it, and it’s velocity (which is constant due to the lack of a (net) force) and location is irrelevant.
So if the train the person is walking on goes around a corner, or slows down or speeds up, then there is a force acting on the frame, and on the person walking – and the frame is no longer ‘inertial’.
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