0.21kg pine cone falls 14 m to the ground, where it lands with a speed of 13 m / s. (a) with what speed would the pine cone have landed if there had been no air resistance? (b) did air resistance do positive work, negative work, or zero work on the pine cone? explain

answer:

ok so not do not trust me on this but here is my answer

(a) if the pine cone would hvve landed with no resistance then it would maintain a uniform speed which in the question is 13 m/s

(b) air resistance generally does negative work but in this case it did zero work

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.