How does inertia affect the ketchup in the bottle?

Answer 1

Inertia is the reluctance of a body at rest to start moving or a body in motion to come to rest. In this case Inertia prevents the ketchup from flowing.

That is why removing/getting it out of the bottle is effective in this way:

1) Hold it by the neck

2) Turn it upside-down (cap ON please)

3) Swing it in this position towards the plate

4) Jerk it to a stop quickly right before it hits the plate

The ketchup will continue flying towards the other end, even though the bottle has stopped. This is because the innertia (or tendency of an object to stay in its current state of motion, at rest or in motion) keeps it moving even though the bottle has stopped.

This is a neat way to do it if this is you Physics Homework for the day, cheaters!

Answer 2

Inertia causes the ketchup to resist changes in its state of motion, so when you try to get the ketchup to come out of the bottle by squeezing it or tapping it, the ketchup initially stays in place due to its inertia. Once enough force is applied to overcome the inertia, the ketchup starts to flow out of the bottle.