The density of water is 1 g/cc. ice floats on water with 90% of its volume
inside the water. what will be the mass of a cube of ice of side 3 cm?

Explanation:

This is pretty easy to calculate when you realize that the mass of the water displaced is equal to the mass of the object floating in it.

Take an iceberg of volume V. It has density d_i. So its total mass is V*d_i = m.

Now, it is displacing 90% of its volume. The sea water has a d_w. The total mass of water displaced is 0.9 * V * d_w, and it equals the mass of the iceberg, V*d_i.

Divide both sides by V. You get 0.9 * d_w = d_i. Now we just have to solve for d_w. Dividing both sides by 0.9, you get d_w = d_i/0.9.

24.3 g

Explanation:

According to Archimedes principle,

buoyant force = weight of liquid displaced

Density of the object floating in a liquid = density of the liquid * fraction of the object inside the liquid

Mathematically represented thus:

ρ(object) = ρ(water) * fraction f

ρ(water) = 1 g/cc, fraction of the object inside the liquid  = 10% = 0.1

ρ(object) = 1 × ( 1 — 0.1 ) = 0.9 g/cc

ρ(object) = 0.9 g/cc

To get the mass of a cube of ice, we use the formula M = ρV

ρ = 0.9 g/cc , L = 3cm, V = L^3 = 3^3 = 27 cc

M = 0.9 * 27

M = 24.3 g

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide