What is the net force acting on the airplane? 740 N right -->
700 N right -->
100 N left <--
760 N right -->

Total force acting on right side = 800 N

Total force acting on left side :

Now, equivalent force acting on the plane is :

And the direction of equivalent force will be the direction of greater force, that is right direction.

Hence, Correct option is :

pe = weightxheight = 2000x1000=2,000,000joules

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.