. You have two carts, one which is empty and has mass m. The second cart is of the same mass but loaded with twice the mass of the empty cart i. e. it has mass 3m. You push each of them (one at a time) with the same constant force, over the same distance, starting from rest. After you have pushed them through this distance, you remove the force. How will the kinetic energy of the loaded and empty carts compare to each other

Their kinetic energies would be the same

Explanation:

This is because, since the force, F acting on them moves the same distance, d, the work done by the force is W = Fd.

Now, from work-kinetic energy principles,

W = ΔK where ΔK = change in kinetic energy of the carts.

Since the work-done is the same for both carts, their change in kinetic energies would also be the same.

Since they start from rest, ΔK = K' - K =  K' - 0 = K'

So, the kinetic energies of the carts would be the same

i think the answer would be b

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.