Question

13. Aluminium foil in the form of a vessel floats on water. But the same foil when folded sinks in water.

a) Is there any change in the density of aluminium foil, if it is in the form of vessel or in the folded form?

b) What is the reason-for the aluminum foil vessel to float and the folded foil to sink?

c) If a folded aluminum foil floats on a liquid, then what is the relation between the density of the liquid and that of aluminum?

Answer 1

Explanation:

Aluminium, iron etc in bulk shape, are denser than water and they will sink.

If the same amount of metal is shaped as a boat, it will float happily on water.

If W is the weight of an aluminium (foil, in your case) and B the weight of the water displaced by the aluminium mass, then the net buoyancy (NB) is equal to:

NB = B - W

If the NB is positive, the aluminium will float, if NB is negative it will sink.

Since W can not change, we can only change B by shaping the aluminium in a way to displace more water, i.e. "building" a boat.