When an empty bottle is closed air tight and pushed inside water it bounces back when it is released. This is because _______.

Correct option is C

Correct Answer: (c) Upthrust of water on a bottle is greater than the gravitational force acting on the bottle

Explanation:

• When an empty bottle is pushed underwater, the upthrust (buoyant force) exerted by the water on the bottle is greater than the gravitational force acting on it.
• This difference occurs because the bottle is filled with air, making it lighter and less dense than water.
• According to Archimedes' principle, the upward buoyant force is equal to the weight of the water displaced by the bottle.
• As a result, the bottle bounces back to the surface when released.

Other Options:

• Water does not exert force on an empty bottle: Incorrect, as water exerts an upthrust (buoyant force) on the bottle.
• Gravitational force on a bottle is equal to the buoyant force of the water: This equilibrium condition applies when an object is neutrally buoyant, but here, the upthrust is greater.
• Gravitational force acting on the bottle is greater than the upthrust of water: This would cause the bottle to sink, which does not happen in this case.