A backpacking physics riddle

“While hiking up Outlook Mountain in the Catskills on my way back from a little overnight trip, a puzzle occured to me.

I wondered the following little scenario: Joe Schmo is a backpacker who weighs 200 pounds. He starts dieting and loses 30 lbs, so he now weighs 170 lbs. During the time it took him to get his weight down, he retained all his strength through a light exercise routine.

Now, if his strength was the same as it was before, shouldn't carrying a 30 lb. pack with him into the woods be the same effort as if he weighed his original weight at 200 lbs.?

Anybody good with physics have any insight?”

“F = ma”

“I'm about 180 lbs. So whem I'm BPing I weigh 200 - 205 lbs. I still keep the same strength. I could handle being over 200 pounds but I'm glad I'm not.”

“Artex, a chart that shows calories burned per hour of walking will show a 200 pound man burning more calories than a 170 pound man. If the man adds 30 lbs to his back, to bring him up to 200 lbs again, I still think it takes less effort, because he is not pumping blood and fluids through those extra 30 lbs.”

“you callin me fat!! how dare you!”

“Splash - that makes sense. Very interesting.”

“As someone who has lost about seventy five pounds in the past year or so let me tell you...

IT IS WAY EASIER BEING LIGHTER! The stress on your body of carrying extra weight on it's frame, feet, etc is incredible. The difference is amazing, even in small amounts like 10#s.”

“how did he loose 30#'s and maintain his strenght?where did he get the $5 pack that allows him to not even feel the thirty #'s?where did he meet the beautful girl that carries the 85#'s plus beer?what is physics?”

“F = ma"
Biz

Biz gave you the answer. However, his weight loss will mean that he is moving 30 pounds less of body weight.


I hate to tell you how many times I've lost 30 pounds or more. Most of the times it has been backpacking on 700 or fewer calories per day. But I don't believe that I've ever had my backpack down to 30 pounds.”

“He actually lost 40 lbs of fat but gained 10 lbs of muscle through the weight lifting program!”

“I got my pack down to 20 lbs for weekend trips Ü”

“Yeah, 30 lbs. is very doable for short trips. Besides, just a hypothetical scenario. :-P”

“Biz, is that with food and water, or without?”

“Pack-- 3.5 lb
Sleeping bag-- 2 lb
Thermarest-- 1.75 lb
Tent & ground cloth-- 4 lbs
Water-- 6.5 lbs
The rest?-- 15 lbs

I'm still working on the weight issue, obviously.”

“Splash is right!

It would be less work for the body!

8)”

“The thing with 30 extra pounds of body weight versus an extra 30 lbs of pack weight is simple, distribution. When haulin fat you get man boobs, chubby ankles and a roll of fat on your neck, even distribution. When adding 30 lbs to your pack you get a big cardboard box filled with 24 cans of beer which is hard to pack evenly.”

“24 cans of beer only weighs 30 lbs?

Jeez I know what I'm packing for the Sipsey trail maintenance trip!”

“I am merely gestimating here, please consult www.drunkhinker.com
or www.stumblindrunk.org........”

“The problem can not be ditermined.

Biz's formula witch I have just been studding for the past month of force is equal to mass time accleration, but to have accleration you need the formula A= Delta, Delta= Final velocite minus initial velocity, but we can't find velocity because we do not have the key componet to velocity's equation of V=D/T Velocity is equal to DISTANCE over TIME, witch we don't have. However a comen technique in SATs is to assicne randome numbers to the appropreat areas to figure out the problem:

Fat guy's force:
Initial Velocity
V= D/T
V= 1m/3hours
V= 0.333
Final Velocity
V= D/T
V= 2m/3hours
V= 0.666

A=Delta
A= FV - IV
A= 0.666 - 0.333
A=0.333

F=M*A
F=200lbs * 0.333
F=66.6
---
For this problams sake the fat guy and the skinny guy are doing the same milage in the same time, however we no it to be true that if you are healthy you hike faster

---Lighter guy
Lighter Guys force:

Initial Velocity
V= D/T
V= 1m/3hours
V= 0.333
Final Velocity
V= D/T
V= 2m/3hours
V= 0.666

A=Delta
A= FV - IV
A= 0.666 - 0.333
A=0.333

F=M*A
F=170lbs * 0.333
F=56.61
-----
Takes less force to move lighter guy.”

“"Weight = Mass x Gravity" if my mind serves me correctly.”

“Weight has nothing to do with this problem. THe only other formulas other than the ones already spoke of my me that could partain to this problem would be the work, and power equations.”

“Yikes, all this physics makes my head spin. I'm more interested in your trip to the Catskills. I'm looking for a weekend getaway and the Catskills might fit the bill. Got any info?”

“Birch nailed the main problem (with the humor added in). The mechanics will be very different due to the difference in the distribution of his weight.

The increased efficiency as the guy gets in better shape, including the effect mentioned by Splash of having less tissue to take care of (circulte blood through, etc...) also plays a role.”

“"shouldn't carrying a 30 lb. pack with him into the woods be the same effort..."

Moving a 30# pack a given distance will require the same energy regardless of the man's weight, if a friend carrys it, if it is caried on a horse or a pack mule, a motorized vehicle, or even shot out of a cannon.

If the man is 30#'s heavier, it will require more energy for the man to move himself.

"...shouldn't carrying a 30 lb. pack with him into the woods be the same effort as if he weighed his original weight at 200 lbs.?"

The question appears ambiguous to me! So,

to move the pack: same energy
to move the man and the pack: less energy at his lower weight.”

“Yeah... what Birch said.”

“If Weight had nothing to do with this problem, then how's come you used it instead of Mass like your equations state should be used?

This query begs the age-old question..."Should I reduce my packweight, strengthen my muscles, or reduce my bodywieght?"”

“You must look a density and momentum to complete the analysis. A light bper with a heavy backpack has a higher mass to volume ratio while a fat dude has a very low one. This means that the mass of the light hiker is more concentrated while a fat dude has it more spread out. This translates into the fat man having a larger radius. When beginning motion, the light man's center of force is very close to the center of mass and maximum radius of mass. When a fat man starts out, he has a large amount of mass at a relativly large distance away from the center of force. This means that a torque is applied by inerta. The material at the maximum radius does not want to move according to inerta, so a torque must be applied to rotate it into normal position. This also occurs when stopping and is recognizable by sloshing. Women also experience this, but it is reffered to as bouncing.”

“Yea- It always gets back to the bounce-doesn't it.”

“Pennsy Hiker - Yes, the trip was great! I hit Echo Lake in the N.E. part of the Catskills, just north of Woodstock. Beautiful area, but I would HIGHLY recommend taking the Wittenberg-Cornell-Slide route. You can take the full loop and it's about 15 miles long, if I remember right. I solo'd that trail about a year and a half ago, and it was fantastic. Terrific views, changing ecosystems with the higher elevations, and pretty darn challenging. I've done that route twice now, and may do part of it again this week for just a dayhike. If you'd like more info feel free to e-mail me at artex_ny@yahoo.com . I'll be happy to answer any questions that I can.”

“..."Should I reduce my packweight, strengthen my muscles, or reduce my bodywieght?""
Buddur
09:45:27 PM
03/31/02


That's an easy question for me, the answer is a resounding-

YES

”

“I agree, Pathman.. I've recently taken up running again, and noticed I wasn't sucking wind nearly as hard this weekend as I would have before. It's what prompted my train of thought which led to the question on this thread.”

“I've been walking a mile and a half as many days a week as I can manage to. I'm hoping to see some improvement this coming weekend in the Sipsey, although this isn't going to be a "big miles" weekend.”

“Another way of reducing pack weight is to fill any excess room in your pack with helium balloons. With a big enough pack you could have a negative pack weight.”

“helium balloons !!!-

No 'real backpacker' would stoop to helium balloons.

Nice idea, though.”

“Yeah, I would jog too, if it wasn't for the bouncing issue. Backpacking is far less painful.”

“A case of beer weighs 18 pounds.”

“Wow Ice Tea! you may not have the language gene, but you got extra mathmatics instead

PROPS!”

“You say you lost 30 lbs. and exercised lightly. I know if you simply diet and don't exercise, you'll lose 50% body fat and 50% muscle tissue, then if you regain those pounds, it's likely they'll come back as fat tissue. Be sure to keep the exercise up.”

“LOL

This has to be the "Funniest Thread on the Web"! From an engineers point of view!”

“Kleetn - Actually, the scenario I preposed was hypothetical. I weigh about 205 lbs, but am six foot one and have slightly below body fat levels, for what it's worth. Still, the fat I do have seems to be concentrating itself at my gut. However, the running regime supplemented with hiking is taking care of that. Lifting weights again is also on the horizon.”

“Thanks for the info Artex. Hopefully, I'll get up there this weekend.”

“lost 75 pounds in the last year!!!!!! Having seen her posted pic's, it's hard to believe she was ever overweight. Is this true Birch? If so, congrats, that's great. If I could just get doen to 180 I would be happy. I think I weighed aboiut 155 when I graduated from high school.”

“Chief, yes she lost that much weight. She also had a baby 14 months ago.And she has worked hard to shed the baby weight and then some.”

“the skinny guy used Phen Fen to loose weight, sued the pharmaceutical company, received a multi million dollar settlement and hired someone to carry his pack.

End result and answer to the problem:

skinny guy uses less effort to backpack.”

“"Effort" is not a physical measurement. The question is flawed.

Try measurable essences such as work, energy, or force.”

“Well, hello mister fancypants...”

“The energy and force would be equal for the man with a 30 pound pack and less fat. Movement of equal weight will take equal force. The differance being how it is distributed. The slimmer man with a 30# pack will just fell the force in differant muscles. Think of calories. A candy bar may have 300 calories. now think about eating 300 calories in lettace. Its the same amount in calories but the lettace takes more effort to consume. Now for the big question If a case of beer weighs 18 pounds how much does a case of lite beer weigh?.”

“That's a lot of lettuce, BAMA.

I dunno about the beer, but I'm willing to find out!”