Question

A 2.8 kg rectangular air mattress is 2.00 m long, 0.500 m wide, and

Answer 1

First off, we have to assume that the 2.8 kg mass of the air matress includes both the material that the matress is constructed from and the air that is contained within.

The mattress can support a total weight that is equal to the weight of water that the air matress displaces.

The volume of the air mattress is:

V(mattress) = (2 m)(0.5 m)(0.1 m) = 0.1 m³

This volume is equal to the maximum amount of water that the matress can displace in the water before it begins sinking.

The density of water is 1000 kg / m²

The weight of the maximum amount of displaced water is:

V(matress) * (density of water) * (g) = (0.1 m³) * (1000 kg / m³) * (9.81 m / s²) = 981 N.

Let m represent the mass that the matress is supporting.

The total weight of the matress and the supported mass is:

(2.8 + m) * 9.81

Setting this weight equal to the weight of the water displaced gives:

(2.8 + m) * 9.81 = 981

2.8 + m = 100

m = 100 - 2.8

m = 97.2 kg