Rock at the top of a 20 m tall hill the rock has a mass of 10 kg how much potential energy does it have

2000Joules

Explanation:

Potential energy is the energy possessed by a body by virtue of its position. A body thrown upward covered a particular height(h) and under the action of gravity(g)

Potential energy = mass × acceleration due to gravity × height

Given mass = 10kg g = 10m/s² height = 20m

Potential energy= 10×10×20

Potential energy = 2,000Joules

Potential energy

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

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.