Require physics help

[USSEnterprise]

One of the few extracurricular activities I am involved in at school is the Cardboard Canoe team. This involves competing in a series of races against other cardboard canoes. The first part of the competition is based on a 3 minute verbal and visual presentation (no powerpoint allowed.) I would like to, for this presentation, to find out how fast our boat is capable of going, based on the mass of the loaded boat, the mass of the paddle, and the amount of force being exerted on the water by the paddle. My estimates for these are:
mass of boat: 135kg
Mass of paddle: 5kg
Force being exerted on water: Approx 20 lbs or about 90N per stroke
There is only one paddler per boat, with a single, double sided paddle.

[Grasshopper]

You need a lot more information to do the calculation. For a start the effect of water and air resistance, both of which (I believe) go up exponentially with speed, and both of which are dependent to a degree on the shape of the boat.

Once the drag effect of air and water resistance equals the force exerted by the paddle, the canoe will stop accelerating. But calculating the speed at which that happens will involve a pretty advanced engineering calculation and a lot more variables than you've given.

[Ed_McCarron]

You need a lot more information to do the calculation. For a start the effect of water and air resistance, both of which (I believe) go up exponentially with speed, and both of which are dependent to a degree on the shape of the boat.

This is physics class.  Aren't we allowed to assume we're in that perfect physics world where theres no friction?

Seriously,  you'd need to know the mass of the paddler, water displaced, surface area under water, shape of the canoes frontal area,  temperature of the water, density of water at that temp, etc, etc, etc.

Tons of variables.

Which ones do they let you neglect?

[shardian]

That is more of a fluid mechanics problem. Definitely more complicated than a simple high school physics problem. I might have my fluids book sitting around - I'll look today.

[USSEnterprise]

Probably a nevermind then. One part of the presentation is to explain the "mathematics and physics" of the design. I need to figure some information out for that.

[shorthair]

You said what you'd like to do. What is the verbal presentation for?

[SirPeale]

If you can't dazzle them with brilliance, baffle them with ---That which is odiferous and causeth plants to grow---.  Make something really complicated up.  Go into all those details (weight of rower, air density, etc).  Betcha get an A.

[danny_galaga]

One of the few extracurricular activities I am involved in at school is the Cardboard Canoe team. This involves competing in a series of races against other cardboard canoes. The first part of the competition is based on a 3 minute verbal and visual presentation (no powerpoint allowed.) I would like to, for this presentation, to find out how fast our boat is capable of going, based on the mass of the loaded boat, the mass of the paddle, and the amount of force being exerted on the water by the paddle. My estimates for these are:
mass of boat: 135kg
Mass of paddle: 5kg
Force being exerted on water: Approx 20 lbs or about 90N per stroke
There is only one paddler per boat, with a single, double sided paddle.

the mass of the paddle doesnt really matter. at least not as much as the surface area of the part of the paddle actually doing the work. dont know much about hydrodynamics, but you will definitely have to know how much drag there is. the drag is exponential. this is how it looks for air pressure: dynamic pressure = 1/2rho V squared. same kind of thing as kinetic energy= 1/2M V squared.

[missioncontrol]

so if canoe A is leaving the docks at 8:45 and paddling 45 strokes per minute and canoe B which is 4 miles downstream leaves the docks at 10:17 and paddling at 28 strokes per minute, what time do they eat lunch?

[USSEnterprise]

The answer is 42

[USSEnterprise]

Now I am trying to find the approximate drag of the boat using the following formula:
F_d = 1/2pb²AC_d

F_d = force of drag
p = pressure of fluid
v = velocity relative to fluid
A =  reference area
C_d =Drag coefficient

What is the reference area?

[rockhopper]

The reference area is the frontal area presented. Ie for a sphere the frontal area would be a circle.

You should note, that the drag on a partially submerged hull will also depend on the bow wave produced. It takes energy to produce the bow wave, and this energy is effectively added to it's drag.

If you look up and decent fluids text on Froude numbers and their relation to drag it will help.  Note that any calcs you do will be a very rough estimate and won't give you anything useful.  I'd just concentrate on the theory behind the drag,  rather than the specific numbers.

Hope that helps

[Zero_Hour]

so if canoe A is leaving the docks at 8:45 and paddling 45 strokes per minute and canoe B which is 4 miles downstream leaves the docks at 10:17 and paddling at 28 strokes per minute, what time do they eat lunch?

Time is an illusion. Lunchtime doubly so.

[Ed_McCarron]

so if canoe A is leaving the docks at 8:45 and paddling 45 strokes per minute and canoe B which is 4 miles downstream leaves the docks at 10:17 and paddling at 28 strokes per minute, what time do they eat lunch?

Time is an illusion. Lunchtime doubly so.

Since we're on that topic...

[danny_galaga]

Now I am trying to find the approximate drag of the boat using the following formula:
F_d = 1/2pb²AC_d

F_d = force of drag
p = pressure of fluid
v = velocity relative to fluid
A =  reference area
C_d =Drag coefficient

What is the reference area?

you are going to have some difficulty seeing as how velocity isnt actually in the above formula 

yes, i can see that the B is supposed to be velocity

[Ed_McCarron]

Now I am trying to find the approximate drag of the boat using the following formula:
F_d = 1/2pb²AC_d

F_d = force of drag
p = pressure of fluid
v = velocity relative to fluid
A =  reference area
C_d =Drag coefficient

What is the reference area?

you are going to have some difficulty seeing as how velocity isnt actually in the above formula 

yes, i can see that the B is supposed to be velocity