Do heavier people go downhill faster?

[Thumper]

Smoke em up the hills, then show some compassion and let them catch you on the way down.

[TCRCARBON]

I have lost 20kg in the past three months.  I cannot keep up with some of the guys I used to ride away from on the steep descents.  That said I am only seconds behind whereas I am minutes ahead of them on the climbs which we used to ride up together.  To balance out my loss of speed I bought some Zipp 404's and we're back in the lead on the downhills as well!

[Borriz]

Bliksem! 20kgs in 3 months!!!!!! Gastric bypass? Keep your diet a secret and sell it for millions

[Black_Jack]

From a purely scientific perspective - if you take away the effect of air resistance there should be no difference...Galileo proved this many years ago by dropping a light and heavy ball off the tower of Pisa.

 

In practice heavier people do descend faster though. This is because their mass creates a down-ward (which translate to forward on a downhill) force much bigger to the up-ward or back-ward force of air resistance. With lighter people the same thing happen, just that the air resistance (which is related to your size and not weight) is bigger in proportion to the downward force created by weight.

 

So - if you're light - sit VERY close to someone bigger in front of you, hope they don't fart, and you should be able to keep up if you can cut out the effect of air resistance.

 

[whistler]

From a purely scientific perspective - if you take away the effect of air resistance there should be no difference...Galileo proved this many years ago by dropping a light and heavy ball off the tower of Pisa.

In practice heavier people do descend faster though. This is because their mass creates a down-ward (which translate to forward on a downhill) force much bigger to the up-ward or back-ward force of air resistance. With lighter people the same thing happen' date=' just that the air resistance (which is related to your size and not weight) is bigger in proportion to the downward force created by weight.

So - if you're light - sit VERY close to someone bigger in front of you, hope they don't fart, and you should be able to keep up if you can cut out the effect of air resistance.
[/quote']

 

This example of Galileo only applies to freefall of objects of different mass does it not?

[whistler]

In freefall: E(potential) = mgh. (mass x gravity accelleration constant x height above ground)

 

and E(kinetic) = 0.5 x m x v^2 (0.5 x mass x velocity squared)

 

thus from the conservation of energy law = Ep must equal Ek

 

thus mgh = 0.5mv^2

 

so this cancels the mass and you get to v = sqaure root(2xgxh)

 

Thus in freefall, mass of an object plays no part... 

[IdeJongh]

In freefall: E(potential) = mgh. (mass x gravity accelleration constant x height above ground)

 

and E(kinetic) = 0.5 x m x v^2 (0.5 x mass x velocity squared)

 

thus from the conservation of energy law = Ep must equal Ek

 

thus mgh = 0.5mv^2

 

so this cancels the mass and you get to v = sqaure root(2xgxh)

 

Thus in freefall' date=' mass of an object plays no part... 

[/quote']

 

Yes but when you ride downhill you dont freefall, in other words freefall has only one reaction force - wind resistence.  When riding the reaction force from the road is not just upward but projects you foward, thus the bigger the mass, the bigger the forward force.

 

Even your terminal velocity would be bigger for bigger okes (think force triangle), big weight (down)= bigger forward reaction force, and thus to reach equilibrium, a bigger resistance is needed (rolling and wind). 

[whistler]

yes i know, was only commenting on the Galileo example given by Black Jack.

 

On a bicycle a bigger oke goes faster downhill for sure!

[IdeJongh]

All good.

[whistler]

 same here. there must be some definite formulas and stuff to support this? the heavier going faster, struggling to think from the top of my head now... 

[Black_Jack]

going downhill in terms of physics is the same as free-falling "at a slope"

 

If you are free-wheeling down a slope, the only acceleration acting in a forward direction is gravity - and that' s the same for big and small okes.

 

Check this link

 

http://www.thenakedscientists.com/HTML/content/questions/question/1843/

 

[Yang]

You can do an experiment to prove that the heavier object will go downhill faster.

 

Get a smooth (polished) board. Incline it to whatever degree you want. At the top end place two boxes of matches, one empty, and one with coins. At the bottom have someone with strong lungs. Let the match boxes go and the oke at the bottom must blow at the boxes (ie, simulating wind resistance). The box with the coins will get further faster, unless the empty box farts and overtakes.

[Gillie]

Yes

[greatwhite]

We accelerate faster on the downhills' date=' but once terminal velocity is reached I think we are all the same - we just get there faster.[/quote']

 

Not quite - terminal velocity for a larger rider is usually higher too. Terminal velocity is the point at which the accelerating force of gravity is equal to retarding force of drag. Since the ratio of drag to mass is usually lower for a larger rider, terminal velocity is higher. i.e. the big will continue to open the gap on the down hill (or continue to catch the flyweight the dropped him on the uphill)

 

Its about the only good news about being a big guy when cycling

 

 

[Tumbleweed]

would a smaller dude be able to corner faster downhill?

[IdeJongh]

would a smaller dude be able to corner faster downhill?

 

Would a fat dude be able to then corner faster uphill?

IdeJongh2009-11-23 05:07:42