"Energy is mv^2 so definitely square of velocity" that is your kinetic energy, which is important for determining acceleration (i.e. braking, speeding up), but not relevant to the power needed to maintain a constant velocity.
"Drag from wind may be v^3 but I didn’t learn about that." It's not, but it's important to define a few terms here: 1. Force is the thing needed to accelerate a given mass : F = m * a [This is measured in pounds/Newtons] 2. Energy (or work) is a force over a certain distance: W = F * d [This is measured in Joules/kilocalories] 3. Power is a work done over a certain period of time: P = W / t = F * d/t = F * v [This is measured in Watts] The *"drag from wind*" is a force and it is a function of the square of the velocity (F_drag = C_drag * A * v^2). But the Power needed to overcome this drag force is that force multiplied by the velocity again (as above P = F * v: So P_drag = F_drag * v = C_drag * A * v^3). So again, the power needed to overcome air resistance goes by the velocity cubed. You can change your coeffecient of drag (C_drag) and your frontal area (A) by crouching on the bike. Drop bars are *hands down* the best way to do this. (Pun intended :) The full equation for power needed over come air, slope, and rolling resistance looks something like this: P_total = C_drag * A *(v_ground + v_wind)^2 + m * g * (C_slope * C_rolling)] * v. To quote David Gordon Wilson in the 3rd edition of Bicycling Science: "This was known a century ago." I'll raise him a bit; the physics was known since at least Euler and Newton's time, so probably closer to three centuries ago. On Friday, May 16, 2025 at 9:53:56 AM UTC-7 [email protected] wrote: > There's a chart here that describes the power required to ride at any > given speed for various positions on a bike (aerobars, drops, hoods, tops, > and standing): > https://ridefar.info/bike/cycling-speed/air-resistance-cyclist/ > > You can see that the standing position is clearly a lot worse than the > others, and that the article claims that the difference between the tops > and the drops is about 1kph or 0.6mph. That doesn't sound like a lot, at > 15mph 70% your power is going into overcoming air resistance. ( > https://maa.org/math-values/2018-7-19-devlins-angle-post-1-sf48y-x6edp-l56an/#:~:text=What%20the%20math%20tells%20you,accounting%20for%20the%20other%20half) > .) > > I guess what this tells me is that I should try lowering the handlebars on > my son's Roadini. > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/5796e1f0-6fc2-4122-9023-4401abfad52bn%40googlegroups.com.
