A50- kg pole vaulter running ar 10m/s vaults over the bar. her
speed when she is above the bar is 1.0 m/s. neglect airresistance,
as well as any energy absorbed by the pole, anddetermine her
altitude ads she crosses the bar.

5.05 m

Explanation:

Given:

According to the work-energy theorem, work done by the gravitational force will be equal to the kinetic energy change in the vaulter.

Hence, the height of the vaulter is 5.05 m.

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.