Section C Floatation ,Very Short type

Very Short Answer Type Questions

1. State the principle of floatation.

An object floats in a liquid if its weight is equal to the upthrust exerted by the liquid.

2. When a piece of wood is suspended from the hook of a spring balance, it reads 70 gf. The wood is now lowered into water. What reading do you expect on the spring balance?

The reading will decrease because of upthrust (apparent weight = 0 when floating).

3. How does the density ρ_s of a substance determine whether a solid piece of that substance will float or sink in a given liquid of density ρ_L?

If ρ_s < ρ_L, it floats. If ρ_s > ρ_L, it sinks.

4. A body floats in a liquid with a part of it submerged. Is the weight of the floating body greater than, equal to or less than upthrust?

Equal to upthrust.

5. What can you say about the average density of a ship floating on water in relation to the density of water?

The average density of the ship is less than that of water.

6. Two identical pieces, one of ice (density = 900 kg/m³) and other of wood (density = 300 kg/m³) float on water.
(a) Which of the two will have more volume submerged?
(b) Which of the two will experience more upthrust due to water?

(a) Ice will have more volume submerged.
(b) Both experience equal upthrust (equal to their weights).

7. A piece of ice floating in a glass of water melts, but the level of water in the glass does not change. Give reason.

Because the volume of water displaced by ice equals the volume of water formed when it melts.

8. A buoy is held inside water contained in a vessel by tying it with a thread to the base of the vessel. Name the three forces that keep the buoy in equilibrium and state the direction in which each force acts.

1. Weight (downward), 2. Upthrust (upward), 3. Tension in thread (downward).