During a football game, a receiver has just caught a pass and is standing still. Before he can move, a tackler, running at a velocity of +5.20 m/s, grabs and holds onto him so that they move off together with a velocity of +2.90 m/s. If the mass of the tackler is 129 kg, determine the mass of the receiver. Assume momentum is conserved.

mass and volume are the answers you are looking for

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.