Aball with a mass of 3kg is dropped from the top of a building this is 20m high. what is the velocity of the ball when it is 10m above the ground ?

Velocity=14[m/s]

Explanation:

We can solve this problem by using the principle of energy conservation, where potential energy becomes kinetic energy.

In the attached image we can see the illustration of the ball falling from the height of 20 meters, at this time the potential energy will have the following value.

When the ball passes through half of the distance (10m) its potential energy will have decreased by half as shown below.

If we know that potential energy is transformed into kinetic energy, we can find the value of speed.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.