Comments on: Sledding

By: Belberith

Belberith — Thu, 20 Aug 2009 18:39:27 +0000

In the diagram, the equation used (for the sledding problem) is rounded. the actual equation derived from ?F=MAy is V=?(2gh) where “g” is ~9.80665 m/s² and “2g” is actually 0.3867 m/s² less than 20 m/s². As a result, the answer from V=?(20h) is larger than the true solution.

(Randall, I think that you already know this)

By: medyum

medyum — Fri, 10 Jul 2009 10:16:58 +0000

No slope though, so it makes sense that the sled would only decelerate at a slower pace. But for the sixteenth of a second it would take to fall through the iced section and hit the water below, the sled would have a momentary boost in total velocity (again assuming that the ice is perfectly horizontal.) Plus, in a really shallow pond (That is, the depth of the water is less than the height of the sled) would the sled go faster, even in liquid water? Hydroplaning?

By: Nick

Nick — Fri, 01 May 2009 14:16:57 +0000

@ Steve-O or if the 88 mph could be achieved on a delorean on a treadmill

By: madkathy

madkathy — Wed, 29 Apr 2009 16:38:53 +0000

I realize I’m late to the party, but the chemist in me can’t resist pointing out…
@Andrew Humid air is not more dense than dry air; it’s actually less dense. The number of gas molecules/volume of gas is fixed. This means in humid air, you have exchanged some nitrogen, oxygen, or carbon dioxide molecules for gaseous water molecules, which actually weigh less. (Add up the molecular masses and check if you don’t believe me.) Less weight per unit of volume = less dense.

By: Steve-o

Steve-o — Sat, 18 Apr 2009 07:07:37 +0000

Given that it’s never established as 88mph relative to *what*, I have to wonder if a wind tunnel could activate a timejump. And then whether it would be possible to build a teeny tiny jet turbine to play over the time circuits as needed…

By: Evan Allen

Evan Allen — Mon, 06 Apr 2009 04:31:32 +0000

they actually use gravity to activate a flux capacitor in episode 11 of season 1 of the canonnically disputed Back to the Future Animated Series (circa 1991)

By: Annoying movie watcher at The Rabenstranger

Annoying movie watcher at The Rabenstranger — Sat, 04 Apr 2009 21:02:16 +0000

[...] needs to leave a note at the bottom explaining that in 30 years they should set out a trampoline. (full post) Filed under Uncategorized. | var blogTool = “WordPress”; var blogURL = [...]

By: rob0

rob0 — Tue, 24 Mar 2009 15:58:25 +0000

Great post – I found it while searching for sledding hills in Cambridge. Took my 3 year old daughter out for her 1st time sledding 2 weeks ago. By the way I love how the hill ends in a pond, adds that nice touch of excitement.

By: Me51

Me51 — Wed, 18 Mar 2009 19:44:31 +0000

My personal favorite… >=):

Can never go wrong with a vampire.

By: Hauke

Hauke — Fri, 27 Feb 2009 07:58:00 +0000

Nice things you try and think about when you go sled. xD
I like this.
Interesting that you use meters instead of inch/feet/miles.

Some additional infos about the velocity:
The recommended speed (depends on traffic. in a jam it’s better to drive slower) on highways in Germany is 130 kph (~81,25 mph; 36,1 m/s). The highest allowed speed ever is 250 kph (156,25 mph; 69,4 m/s) but you can’t mostly never reach this. But with a good car and a free road 150-180 kph (93,75-112,5 mph; 41,6-50 m/s) is no problem.