Think energy. http://en.wikipedia.org/wiki/Kinetic_energy http://en.wikipedia.org/wiki/Potential_energy First, SI units please. 30 MPH = 13.4 m/s 200 pounds = 90.7 kg (this is on earth, right?) The moving bike has a kinetic energy of m(v^2)/2, or 90.7*13.4*13.4/2= 8143 joules. Gravitational potential energy is U=mgh. Solving for h: h=U/mg or 8143/(90.7*9.8)=9.2 meters. 9.2 meters is about 30 feet. I probably screwed the numbers up; I always did in physics class. Regards, Mark markrages@gmail On 5/3/06, James Newtons Massmind wrote: > I'm trying to figure out how much force it takes to get the average bicycle > moving (or stopped) and how that relates to the force required to lift the > same mass some distance. > > E.g. if a bicycle and rider weighing 200 lbs total was to decelerate from 30 > MPH to 0 in 5 seconds, how far would that amount of force lift the same > weight into the air? > > 30 mph = 44 feet per second and F = M * A so we are talking about 200*44/5 > right? Or 1760 foot lbs? With 200 lbs, that could then be raised 1760 / 200 > = 8.8 feet? > > If we don't want to fly up 9 feet in the air, how does one figure out how > much force can be stored in a spring of a given weight? I must be using the > wrong keywords 'cause Google isn't doing it for me. I'm thinking about a > flexing flat piece of spring steel, like a single leaf of a leaf spring. > > Maybe I should have started by saying that this is related to regenerative > braking: > http://www.massmind.org/techref/other/regenerativebrakes.htm > > And yes, I know that if I had paid attention in Physics 101, I probably > wouldn't have to bother you all with these questions... > > > --- > James. > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- You think that it is a secret, but it never has been one. - fortune cookie -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist