moldybluecheesecurds 2

Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts

Friday, May 25, 2007

Physics question update: solved!

Thanks to mechanical engineer (and now canoe lift consultant) LH, we've learned several things:
  1. My existing pulley system offers "no mechanical advantage." That's a politically correct way of saying that it did squat. Less friction on the rope, but all the weight of the canoe. Great.
  2. My 12th grade physics class provided me with crackerjack abilities to predict the fall of a marble down a stairwell or launch a 2-liter bottle rocket 75 yards, but no actual life skills.
  3. Fortunately, there are much smarter people than I who do have a clue (example follows).
So, it turns out that the right way to lift a canoe without playing "spin the jff" or "crack the K" is diagrammed here:

You can tell this diagram was made by an intelligent person by the use of subscript to describe the "load." Even a science-dolt like myself can understand that I will be exerting one-third the physical force and 1/10th the mental energy by following this diagram. Thank you, LH.

Update 2, 12:07am: The new system worked and the canoe is currently suspended. Now we just hope that my knot-tying merit badge was legitimately earned. Wait, was I a Boy Scout?

Why we need more physics education

We got a canoe last weekend. A nice find via Craigslist, it even included some lifejackets (aka PFDs), paddles, and a little trailer. K drove 3 hours round-trip to pick it up and we're excited to have our own canoe at last.

Then came the storage issue. The garage door eliminated jff's brilliant plan to hang the canoe over the car, allowing for quick loading/unloading. Canoe must hang sideways. Okay, then we have to clear the rafters of all the accumulated junk from previous owners (hey, nice golf clubs!). Now jff applies his high school physics and gets a couple pulleys. Gee, for some reason, lifting a 60-pound canoe with a thin rope isn't as easy as you would think.

Jff goes advanced - looks up pulleys on Wikipedia. Purchases additional pulleys and constructs a basic "block and tackle" (and slicing thumb with utility knife). In theory, we now only need to exert 30 pounds of force to lift the canoe. (see image)

After a ferocious battle that succeeding in lifting the canoe to the garage ceiling (30 pounds, my ass!), team Canoe Lift could not cleat the rope without dropping the canoe. This failure despite jff wrapping himself in the lift rope like a mummy whilst K attempted to tie it down.

So, those who get physics - help! What's wrong with the pulley system? Is the solution more pulleys (see image below - bonus pulleys in red)? Counterweights? A patch of grass and a tarp?