A mass of 2 kg traveling at 3 m/s undergoes a one-dimensional elastic collision with a group of four 1-kg masses that are at rest in contact with each other and lined up in the same direction as the velocity of the 2-kg mass. As a result of the collision
A) the 2-kg mass comes to a stop and two of the 1-kg masses take off at 3 m/s.
B) the 2-kg mass comes to a stop and one of the 1-kg masses takes off at 6 m/s.
C ) the 2-kg mass and the five other masses travel at 1 m/s.
D) the 2-kg mass comes to a stop and all four of the 1-kg masses take off at 2 m/s.
E) the 2-kg mass comes to a stop and three of the 1-kg masses take off at 2 m/s.

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.