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# M2 Work, Energy and Power watch

1. "A pump, taking water from a large reservoir, is used to spray a jet of water with speed 20ms^-1 and radius 0.05m from a nozzle level with the surface of the reservoir. Calculate the power of the pump"

I have no idea what to do on this question. I know power = force x velocity or energy / time. Where energy = Fs or 1/2mv^2 or mgh. But I can't see a way in. Any help would be appreciated!!
2. IIRC, (had a similar Q to this), you have to use the radius, to work out the volume, and then its mass via the density formula, of water pumped out every second.

Once you know its mass you can work out the work done in pumping the water (upwards I think, so its mass vs. gravity).
3. Work out the volume of water emitted from the pump every second. You know that a cylinder 20m long with radius 0.05m is emitted every second.
Use Density = Mass/Volume to work out the mass of the water and then use your energy relationships to work out the power.

Density of water = 1000 kg/m^3

EDIT: looks like someones beaten me to it :P, took far to long to think that through in my head.
4. (Original post by Thrug)
IIRC, (had a similar Q to this), you have to use the radius, to work out the volume, and then its mass via the density formula, of water pumped out every second.

Once you know its mass you can work out the work done in pumping the water (upwards I think, so its mass vs. gravity).
Okay cheers so I've gotta make the assumption that the density of water is 1000Kgm^-3.

EDIT: Sorted cheers guys

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