Thread: Momentum, Force, cycling and skiing

OK, so I know in a vacuum that a feather will fall to the ground just as fast as an anvil (F=ma). What my simple mind can't figure out is why - when I'm cycling - a portly guy like me will gradually pass the leaner/cooler dudes going down hill?

It's the same deal with Down Hill ski racers, the bigger skiers carry more momentum into the flats (can you say Bode Miller) and, ergo, finish quicker. So I have the momentum thing down [mv]: I have more momentum when I'm cycling than the lean and mean folks. But how do I reconcile the constant acceleration idea. According to Newtonian mechanics - ignoring friction - I should go downhill at the same pace as the little guys???

gravitational force vs Wind restistance. Same as an anvil vs a feather. The force of the air can equal the total force of the feather easily.

mass x acceleration = force. if the wind is blowing two people ( against the direction of movement ) then with an equal force ( assuming same wind resistance ) ... the wind is accelerating a lighter person more.

so with equal wind
100 units of wind can accelerate a 100 k person 1 meters per second ^2
100 = 100k x 1 meters per second ^2
or
100 units of wind can accelerate a 50 k person 2 meters per second ^2
100 = 50k x 2 meters per second ^2

So your downhill momentum in a vacuum will be the same but the wind resistance is decellerating the skinny guy at twice the rate it is the bigger better cyclist.

The same is true for the friction of the bike .... and anyother external forces acting on the cyclist.

Originally Posted by pheadden

OK, so I know in a vacuum that a feather will fall to the ground just as fast as an anvil (F=ma). What my simple mind can't figure out is why - when I'm cycling - a portly guy like me will gradually pass the leaner/cooler dudes going down hill?

It's the same deal with Down Hill ski racers, the bigger skiers carry more momentum into the flats (can you say Bode Miller) and, ergo, finish quicker. So I have the momentum thing down [mv]: I have more momentum when I'm cycling than the lean and mean folks. But how do I reconcile the constant acceleration idea. According to Newtonian mechanics - ignoring friction - I should go downhill at the same pace as the little guys???