7,000 litres of water is pumped out of a tank in 42 minutes. How many litres could be pumped out in one hour at the same rate? (a) 1,000 litres (b) 1,670 litres (c) 10,000 litres (d) 12,000 litres (e) 60,000 litres

electrical power

f=ma newton's second law 7x8=56n

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.