A group of kids come across a covered bridge that is a great spot for jumping off, but they want to make sure they stay safe so they want to check how high the
bridge is before anyone jumps off. They find a 5kg rock and guess that it will
experience a coefficient of friction of 0.21 as it falls. Once the rock is thrown over
the edge of the bridge, it takes 1.6s to reach the water.
How tall is the bridge?

the answer is b ) square root of 5

electrical power

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.