Question

The figure shows three glasses P, Q and R with water and floating ice cube. Glass P has a solid ice cube, glass Q has an ice cube with a small solid steel ball embedded in it and glass R has an ice cube with an air bubble. After the ice cube melts, the level of water in glasses P, Q and R, respectively:

• A. remains same, increases, and decreases
• B. increases, decreases, and increases
• C. remains same, decreases, and decreases
• D. remains same, decreases, and increases

Hint:

Always compare displaced water vs. final water volume after melting; embedded heavy objects reduce displacement after sinking, while air bubbles reduce final water volume.

Answer 1

The Correct Option is C

Step 1: Glass P — pure ice cube.
A floating ice cube displaces water equal to its weight. When it melts, it simply becomes the same mass of water. Thus the water level remains the same.

Step 2: Glass Q — ice cube with steel ball.
The steel ball is denser than water. While the ice floats, part of the ball's weight is supported by the ice, causing extra water displacement. After melting, the steel ball sinks and displaces only its own volume, which is less water than before. Hence the water level decreases.

Step 3: Glass R — ice cube with air bubble.
The air bubble makes the ice less dense overall. While floating, the ice displaces water equal to its weight, which is more volume than the water produced after melting (because melting releases water but the bubble disappears). Hence the water level decreases.

Final Answer: (C) remains same, decreases, and decreases