The velocity of a diver just before hitting the water is -7.7 m/s, where the minus sign indicates that her motion is directly downward. what is her displacement during the last 0.82 s of the dive?

The velocity of a diver just before hitting the water is -7.7 m/s ( i.e final velocity ).

Therefore velocity of diver before 0.82 s,

.

Now the displacement  during the last 0.82 s of the dive, from the vertical motion,

Thus, the displacement is 3.0 m in downward.

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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.