Nice summary of mileage stretching

[thomason2wheels]

Originally Posted by Vman455

I'll rephrase my question: is there a point at which the inertia of a more massive body overcomes the increased rolling resistance of that body such that it will roll downhill faster than an aerodynamically-identical, less massive body? I see people all the time claiming that a heavy car will roll downhill faster than a lighter, but I've never seen any evidence to suggest this is so.

the laws of physics suggest the lighter vehicle with all other variables constant will accelerate to terminal velocity more quickly than the heavier one. Less mass is easier to move.

[bikenfool]

It's basic physics.
F=Ma,
The acceleration due to gravity on a slope is
g*sin(theta) where g is the 9.81 m/s^2 and theta is the angle of the slope
Rolling resistance is approximately Cr*M, M is the mass, Cr is the rolling resistance coeff.
The aero drag force is (1/2)*rho*Cd*A*V^2, rho is the air density, etc
F=Ma=M*g*sin(theta) - Cr *M - (1/2)*rho*Cd*A*V^2
so the acceleration, a is
a = g*sin(theta) - Cr - (1/2)*rho*Cd*A*V^2/M

So you get more acceleration with steeper slope, lower Cr, lower CdA or density, or more mass. You can solve for terminal velocity. I'll bet this is in the wiki isn't it?

[thomason2wheels]

F is a constant...gravity. acceleration is the unknown variable. Solve F/M=A...therefore the larger the mass the less the acceleration. The lighter vehicle accelerates faster all other things being the same. Please tell me you understand what I am saying?

[sendler]

Thanks for sending me to fuelly so I could vote NO for the "cold air intake". I made a new tip. "Hot Air Intake".