How much energy from weight moving.

Question

If I were to harness the energy of 1.7 billion pounds of water dropping 6 feet, how much energy would that be in watts?

If you can tell me how to do the calculation, I'd be really pleased.

Thanks

Answer 1

In this example, the units are given like this:

[Metric] or [imperial]

P = m*g*h

P = energy in joule

M = mass in kg or pounds

g = 9.81 m/s^2   or   32.174 ft/s2

h = height in meters or feet

Or, in your example:

1.7 * 10^9 * 32.174 * 6 = 328 174 800 000 joule

or 328.17 gigajoules

Answer 2

It depends on how long it takes. Watt is energy (1 Joule) per second.

A joule equals 1 pound force over the distance of 1 foot. 1 Joule = .7376 lb*ft

So 1.7 * 6 = 10.2 lb*ft = 13.83 billion Joules. If it falls in one second, thats 13.83 billion watts. over an hour, thats 3840 kilowatt hours, the unit your home electricity is measured in.

EDIT: the above answer is confusing the slug (imperial unit of force), with the common use of "pound force" being the same unit as "pound mass"

Answer 3

First : Energy is measured and expressed in Joules (J) . The Watt (W)is the unit of power.

I cannot work in feet etc, so I will change your question as best I can to SI units:

If I harness the energy of 7.718*10^8kg water dropping 1.8288m how much energy is generated

Potential Energy = mgh

Potential Energy = 7.718*10^8*9.81*1.8288

Potential Energy = 1.385*10^10J

Ek = Ep so this is the energy produced by the water at the bottom of the fall.

If you want an aswer in Watts, which is the power produced, you have to use the equation:

  W = J/t

If we assume that it took the water 1 hour = 3600 seconds to fall, then

W = 1.385*10^10 / 3.6*10^3

W = 3,846,250

Power would be 3.85MW