4. a 3.0-kg block slides on a frictionless 20° inclined plane. a force of 16 n acting parallel to the incline and up
the incline is applied to the block. what is the acceleration of the block?
a. 2.0 m/s2 down the incline
b. 5.3 m/s2 up the incline
c. 2.0 m/s- up the incline
d. 3.9 m/s² down the incline
e. 3.9 m/s2 up the incline

hotter stars = bluer stars

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.