Recent content by jaguar7

Thanks. =) Still, though, how would one go about showing mathematically that energy is the 4th component of momentum, I wonder...?

Hi, tiny-tim. Thank you for your response. I'm afraid I'm not very good with matrices. I suppose I'll have to review that. I've been looking for my old books. They've been mysteriously difficult to find after I moved... I understand that a change in velocity is a rotation between...

Assuming that c is a "conversion factor" to convert between space and time, Then, in 4-vector, we have x_1 through x_3, and t, where, x/c = t x/c = t, (where t = time, c= lightspeed, x = spatial dimension) If we do what we did to space to get time, to momentum, p/c = m*v/c = m (x/t) / c =...

Okay, my bad. Thank you. ^_^ Well, moving forward; we might as well make "sin(a)" "sin[a(r)]" since propeller blades always have the element of "twist." After integrating, and factoring out the constants, that leaves us with: 4∏^2(RPM)^2D/min^2 ∫(0 to r_f): r^2 w(r) sin[a(r)] dr ...which is...

Yeah, I need width as a function of r, since width isn't going to be constant. Which also means I can't use average velocity. You're right. But I'm telling, you, dude - the integral of force with respect to a distance (r) is work. I probably shouldn't disagree or whatever because I don't...

Ibix: if wedo this, like you say: F[v(r)] = Av^2(r)Dsin(a) = wdr [RPM 2∏r / (1 min)]^2 D sin(a), we would still have force on the left hand side. Integrating force would still give us incorrect units... we'd need to do something to fix or accommodate for that... I can't think of what to do...

I'm trying to find the average velocity of a spinning propeller. v(r) = RPM C(r) / t ; C(r) = 2πr; t=(1 min) v(r) = RPM 2πr / (1 min) I'm not quite sure what to do next. I need the answer in units of velocity, but if I integrate that last equation, I won't get units of velocity. My rough...

Okay, the article (and its related articles) don't seem to give me everything I was looking for, and they seem a bit different from what I'd get. I'm wondering if I'd be correct in my reasoning: We could find out the mass per second that collides with the paddle, by the water's velocity, and...

If a paddle of area, A, is submerged in a river of water-velocity, v, and (assumed constant) water pressure, P, the paddle at an angle, m, what is the force exerted on the paddle by the moving water of the river? the paddle is being held still from a bridge...

okay, How do you find delta v (change in velocity)? Given propeller shape, pitch angle, diameter, area, etc. and air pressure? That was actually my original question. For some reason I didn't notice that ⌂v of the air was in the equation you gave. Also, I'm reading the link you gave, and I...

That equation looks oversimplified to me, as it doesn't include angle of attack or area of the airfoil, or anything like that. I had found a seemingly oversimplistic equation before, but at this point, I would like to see a derivation. Additional Information: "Pressure arises because each...

Update: If we can outline a path that the propeller travels over time, then we can calculate weight/time of the fluid it displaces. Weight is a force? Or do we need mass? If a propellor displaces a certain amount of volume of a fluid substance, how do we calculate force, if we know the...

F=force, m=mass, a=acceleration, V=Volume, D=Density, dv/dt=(change in velocity)/(change in time) F=ma D=m/V m=VD a = dv/dt F=VDdv/dt = Volume * Density * (change in velocity) / (change in time) = (Volume of Air Moved) * (Density of the Air) * (the final velocity of the air)...

Okay, I'm wondering what is the max safe amperage I can trickle charge this battery with? Again it's two 12V lead acid batteries in parallel.

I have a battery. I can go get a screwdriver from the garage and open it to see the specs on it, but was for an electric bike. I don't have the AC adapter charger any more. Can I charge it with a universal AC adapter I have, just wired together? The AC adapter has two holes in the tip, and I...