A toy car, initially travelling in a straight line at 30.0 cm/s, slows down with a constant linear acceleration of 3.0 cm/s2. How much time passes before the toy car comes to a halt?

10s

Explanation:

Given parameters:

Initial velocity  = 30cm/s

Acceleration  = 3cm/s²

Unknown:

Time it takes for the car to come to rest  = ?

Solution:

To solve this problem, we apply the right motion equation;

   Our final velocity - 0

So;

       V = U + at

Since the car is slowing down, it will have a negative acceleration

Insert the parameters and solve;

       0 = 30 + (-3) x t

          -30 = -t

              t = 10s

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.