4. A 900-kg compact car moving at 26.7 m/s has approximately 320,000 Joules of kinetic energy. What is its new kinetic energy if it is moving at 13.3 m/s?

79600.5J

Explanation:

Given parameters:

Mass of compact car  = 900kg

Initial velocity  = 26.7m/s

Energy = 320000J

New velocity  = 13.3m/s

Unknown:

New kinetic energy  = ?

Solution:

Kinetic energy is the energy due to the motion of a body.

   Kinetic energy  =  m v²  

 m is the mass

 v is the new velocity

  Kinetic energy  =   x 900 x 13.3²   = 79600.5J

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.

i would say