Arace car enters the circular portion of a track that has a radius of 63 m. when the car enters the curve at point p, it is travelling with a speed of 120 km/h that is increasing at 5 m/s2.

When car enters a circular path its speed is increasing at rate 5 m/s^2

so this is the tangential acceleration of car

now at the same time since car is moving along the curved path so it must have centripetal acceleration at the same time

It is given by equation

so now the net acceleration of the car is given as

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.