Final answer:
The water initially sloshes to the left side of the cup because of inertia. On a roller coaster, your stomach does not actually move up.
Step-by-step explanation:
When a glass of water is moved to the right, the water initially sloshes to the left side of the cup because of inertia. Inertia is the tendency of an object to resist changes in its motion. So, when the glass is suddenly moved to the right, the water inside the glass wants to continue moving in its original direction, causing it to slosh to the left side of the cup.
When going down a slope on a roller coaster, your stomach does not actually move up. The sensation of your stomach dropping or feeling light is due to the force of gravity pulling you downwards, while the roller coaster is accelerating downwards. This creates a feeling of weightlessness or reduced downward force on your stomach, giving you the sensation of it moving up.
Learn more about Inertia and sensation of stomach movement on a roller coaster.