Write an expression for the work done by friction as the block slides from A to B. Your answer should be in terms of m, h, vB, and g (the acceleration due to gravity).

Complete Question

The complete question is shown on the first uploaded image  

The expression is  

Explanation:

Generally the work energy theorem is mathematically represented as

Here   is the potential  energy at A which is mathematically represented as

And   is the kinetic energy at B which is mathematically represented as

So

=>  

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.