I'm supposed to find out how much fuel I need to use to transport a 7kg (max) boat I created.
First I need to find how much energy it uses, and I understand resistance has a great deal of say.
How do I find out the resistance of my boat to the water with the measurements I have?
All I need is a formula... or several if that's the case. It's hard finding this kind of information on the internet..
First I need to find how much energy it uses, and I understand resistance has a great deal of say.
How do I find out the resistance of my boat to the water with the measurements I have?
All I need is a formula... or several if that's the case. It's hard finding this kind of information on the internet..
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Sorry you're outta luck.
You see fluid dynamics is based in large part on coefficients that are found only through experiment and models. As I suspect you do not have the coefficient of drag for your boat, you really can't solve the drag equation and find how much force is needed to push it through the water. So no equations.
But here's what you can do by knowing the physics. Use a fish scale to drag your boat through the water at various speeds. [See source.] Note how many force units (Newtons, pounds) it takes to drag the boat at V speed. Graph the force F vs V^2 for several forces/speeds. You should get a reasonably straight line with a slope dF/d(V^2) = k.
So now you can predict a force F = kV^2 for whatever speed, V, you want to drag the boat at. And F*S = kV^2 S = work done, where S is the distance you want to move the boat with a force F. And if you have the specific energy Cp (joules/kg) of the fuel, the amount of fuel needed in kilograms will be at least N = FS/Cp = kV^2/Cp QED.
Note, "at least" because there will be unaccounted for losses that will add to the inefficiencies. In which case more fuel will be needed to make up for those losses.
You see fluid dynamics is based in large part on coefficients that are found only through experiment and models. As I suspect you do not have the coefficient of drag for your boat, you really can't solve the drag equation and find how much force is needed to push it through the water. So no equations.
But here's what you can do by knowing the physics. Use a fish scale to drag your boat through the water at various speeds. [See source.] Note how many force units (Newtons, pounds) it takes to drag the boat at V speed. Graph the force F vs V^2 for several forces/speeds. You should get a reasonably straight line with a slope dF/d(V^2) = k.
So now you can predict a force F = kV^2 for whatever speed, V, you want to drag the boat at. And F*S = kV^2 S = work done, where S is the distance you want to move the boat with a force F. And if you have the specific energy Cp (joules/kg) of the fuel, the amount of fuel needed in kilograms will be at least N = FS/Cp = kV^2/Cp QED.
Note, "at least" because there will be unaccounted for losses that will add to the inefficiencies. In which case more fuel will be needed to make up for those losses.