Calculating Momentum of a High-Velocity Water Jet?

[ar202]

Homework Statement

A jet of water has a diameter of 30mm and a velocity of 40m/s. Determine the momentum/sec of the water. (Take p to be 10000kg/m³)


this is my first post, apologies if i have missed anything out...

 

[Stonebridge]

Welcome to Physics Forums!

You need to show us some attempt at a solution, and tell us what exactly it is you don't understand, before we can help you?
Do you know the formula for momentum?

 

[ar202]

Ah ok, to be honest I'm fairly lost. Most of the problems I've encountered so far have been to do with impact m1u1+m2u2=(m1+m1)v etc...

i'm not exactly looking for the answer, but perhaps a nod in the right direction :-)

 

[Stonebridge]

If you think of the jet of water as a cylinder of water, what volume of water passes in one second? You have the radius/diameter of the end and you know how long the cylinder is from the speed of the jet.

 

[ar202]

If you think of the jet of water as a cylinder of water, what volume of water passes in one second? You have the radius/diameter of the end and you know how long the cylinder is from the speed of the jet.

Yeah i thought of it that way but then hit a wall...

so the volume is pi*0.015^2*40 = 0.0283m^3 * 1000 = 28.3kg

then is it 28.3 * 40 to get 1132kgms-1 ? is there another step I'm missing?

 

[Stonebridge]

Yeah i thought of it that way but then hit a wall...

so the volume is pi*0.015^2*40 = 0.0283m^3 * 1000 = 28.3kg

then is it 28.3 * 40 to get 1132kgms-1 ? is there another step I'm missing?

That's it. That is the "mv" in one second.
Well done.

 

[ar202]

That's it. That is the "mv" in one second.
Well done.

thanks for your help dude