SOMEONE HEL

How long does a 75kW motor take to extract 400m³ of water from a depth of 150m?

53.33 seconds

Explanation:

From the question;

We are required to determine taken to raise the water from the given height.

We know that density of water is 1000 kg/m³

Therefore;

Mass of water = 400 m³ × 1000 kg/m³

                       = 4.0 × 10^5 kg

Thus, force required to raise the water;

 = 4.0 × 10^5 kg × 10 N/kg

  = 4.0 × 10^6 N

To determine the time;

we use the formula;

 Time = work done ÷ power  

          = (4.0 × 10^6 N × 150 m) ÷ 75000 Joules/s

          = 53.33 seconds

Therefore, time taken to raise the water is 53.33 seconds

think its the third option

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000