Anybody know about Waterjets?

[Keen_Ed]

What I struggle to understand is that a water jet is effective when the jet emerges above the surface, it seems counter intuitive.

Newton's second law. The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd.

The faster you can chuck stuff out the back, the faster the boat will go. You can throw the water faster into air than into water. The waterjet isn't pushing.

 

[alant]

Newton's second law. The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd.

The faster you can chuck stuff out the back, the faster the boat will go. You can throw the water faster into air than into water. The waterjet isn't pushing.

But there will also be less resistance for the jet to push against.

 

[Bertramdriver]

But there will also be less resistance for the jet to push against.

As I understand it Newtons law does not extend to having something to push against otherwise every jet airliner would fall out of the sky. It states that for every action there is an equal and opposite reaction. The faster you squirt something the faster you go. Bit like life really.

 

[rustybarge]

But there will also be less resistance for the jet to push against.

As I understand it Newtons law does not extend to having something to push against otherwise every jet airliner would fall out of the sky. It states that for every action there is an equal and opposite reaction. The faster you squirt something the faster you go. Bit like life really.

Good point. Firemen holding a fire hose don't feel any difference squirting the water into the air, or against a wall...

 

[alant]

Good point. Firemen holding a fire hose don't feel any difference squirting the water into the air, or against a wall...

They would, if the nozzle was directly against the wall!

 

[Keen_Ed]

Put a running hose in a bucket of water, and then pull it out. When do you have more thrust?

 

[Bajansailor]

Here is a good example of how water jets work :

http://www.youtube.com/watch?v=Cd6C1vIyQ3w

 

[Bertramdriver]

Here is a good example of how water jets work :

http://www.youtube.com/watch?v=Cd6C1vIyQ3w

Wow please can I have one for Christmas.