An engineer in a locomotive sees a car stuck on the track at a railroad crossing in front of
the train. When the engineer first sees the
car, the locomotive is 330 m from the crossing
and its speed is 21 m/s.
If the engineer’s reaction time is 0.44 s,
what should be the magnitude of the minimum deceleration to avoid an accident?
Answer in units of m/s
2
.

c because the news are a source of information of things that happen on the daily and shows evidence about that particular topic

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.