A plane decelerates at a constant rate of 3.9 m/s [W]. If the plane's initial velocity was 24 m/s [E], how long does it take for the
plane to come to a complete stop?

t = 6.15 [s]

Explanation:

To solve this problem we must use the following equation of kinematics.

where:

Vf = final velocity = 0 (the plane comes to stop)

Vo = initial velocity = 24 [m/s]

a = desacceleration = 3.9 [m/s²]

t = time [s]

Note: The negative sign of the acceleration means that the plane is decreasing its velocity.

0.55x745.7j and a calculator

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.