A sky diver jumps from a helicopter and is falling straight down at 30 m/s when his parachute opens. From then on, his downward acceleration is approximately
a = g - cv2 , where g = 9.81 m/s2 and c is a constant. After an initial "transient" period, he descends at a nearly constant velocity of 5 m/s.

a. What is the value of c, and what are its SI units?

b. What maximum deceleration is the sky diver subjected to?

c. What is his downward velocity whe he has fallen 2m from the point at which his parachute opens?

a. are

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

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.