A family decided to take a canoe trip one summer. After paddling for an hour, they decided to drift along with the river current to take a break. When they stop, the canoe is traveling east at 1.3 m/s while the river current is moving 0.2 m/s to the west. When the canoe drifts into the path of another river that joins the first, the west-moving current is 0.8 m/s. How will the canoe be affected?

 v_c = 0.7 m / s    east

Explanation:

This is a one-dimensional velocity addition problem.

1 part

The canoe goes to v_ = 1.3 m / s towards the east and the river goes to

v_r = 0.2 m / s towards the west, if we assume that the direction towards the east is positive v_r = -0.2 m / s

the speed of the canoe with respect to the land is the speed of the canoe with respect to the river plus the speed of the river with respect to the land

             v_c = v_{cr} + v_r

             v_{cr} = v_c - v_r

             v_{cr} = 1.3 - (-0.2)

             v_{cr} = 1.5 m / s

this is the speed of the with respect to the river.

2 part

now we enter a river that the speed is v_r = -0.8 m / s, therefore the speed of the canoe with respect to the land is

              v_c = v_{cr} + v_r

              v_c = 1.5 - 0.8

              v_c = 0.7 m / s

the positive sign indicates that it continues to move east

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.