Question

An iron needle _______ in water but a ship _________ on water.

• A. sinks
• B. floats

Answer 1

1. Density of a substance is defined as its mass per unit volume.
2. Density = Mass/ Volume
3. According to the principle of floatation,

• If the density of the solid is more than the liquid, it will sink.
• If the density of the solid is less than the liquid, it will float.

4. Density of iron is more than the density of water, so it sinks.

5. An iron ship is designed in such a manner that it is hollow from within.

6. Thus, the volume of the iron ship is much more than its mass.

7. Since the density of a substance varies inversely with its volume, so the density is iron ship becomes less than that of water.

8. So, the ship floats on water.

9. An iron needle sinks in water but a ship floats on water.