Wikipedia:Reference desk/Archives/Science/2014 September 15

= September 15 =

can you carry your own weight? (briefly, e.g. on your back)
hi,

I was wondering if an average man of 150 pounds could carry 150 pounds on his back briefly (e.g. 100 meters / 109 yards). or is that too hard? 212.96.61.236 (talk) 23:59, 14 September 2014 (UTC)


 * Well, I can think of a couple of 'data points' that say "yes". Soldiers in Iraq were carrying 65lb backpacks, plus (at the outset) 5 gallons of water (50lb) plus weapon, bulletproof vest, helmet and ammo (easily another 50lb) - and they would march many kilometers while loaded to that degree.  So it's certainly possible if you're moderately fit and if the weight is well distributed and positioned appropriately.  A second data point it that there are plenty of people out there who started off weighing 150lb and through poor diet and exercise ended up weighing 300lb or more - and can still get around fairly easily. SteveBaker (talk) 00:17, 15 September 2014 (UTC)
 * I would argue that neither a soldier in iraq, nor a 300lbs person are "average man". However I agree that an average man would quite easily be able to "piggy back" another average man for 100m. I very much doubt however that an "average man" could piggy back another average man for "many kilometers". The answer lies somewhere in between.. Vespine (talk) 00:57, 15 September 2014 (UTC)


 * How much do you suppose an average person can easily carry? (e.g. for kilometers) Online I saw "1/3 of body weight" thrown around - does this seem right? )  — Preceding unsigned comment added by 212.96.61.236 (talk) 01:00, 15 September 2014 (UTC)
 * I weigh about 80kg, 1/3 would be 26kg, I might not be terribly average, I'm not overweight (I'm 183cm tall) but i don't really exercise, so I can't imagine "easily" carrying 26kg for a few kilometers, I'm pretty sure I could do it, but it sounds like a considerable work out to me. Even if the weight was being carried in a decent backpack. If I had to carry it in my arms or over my shoulder, like a sack of potatoes, then no, I don't believe it would be easy at all. it's a tough question, it really depends on what you mean by easy.. Like, if I was stuck in the desert and had only 26L of water then yes I'd be carrying it :) Vespine (talk) 01:11, 15 September 2014 (UTC)


 * My wife can carry a 15 kg pack (25% of body weight) for days at a time when walking and camping. I can carry 22 kg (21%) for days at a time and I doubt I'd be regarded as fit. So 25% is easy enough. Now, if she stuffs her back, I get to carry both packs. That is possible, on the flat, but in any significant terrain it is much faster and more comfortable for me to ferry the packs individually. Although I am walking 3 times as far, once is unladen, and once is lightly loaded. I can do that for 10 km in a day (ie 30 km actually walked) but the next day wouldn't be much fun.Greglocock (talk) 01:44, 15 September 2014 (UTC)


 * A good quality back back that fits properly should allow you to carry your own body weight for a while quite easily. If you are reasonably fit and can run for 30 minutes without gasping for air, you should be able to walk for half an hour with a such a backpack. You do have to get used to it for a while, because you may feel that this is way too heavy, but that's simply because your brain makes an assesment based on the exertion required to stand up and get moving with that thing compared to the speed. You will tolerate a heart rate of 150 bpm much easier when you are actully running fast, compared to when you are just walking. This is all a psychological issue that you have to learn to tolerate. Count Iblis (talk) 03:27, 15 September 2014 (UTC)


 * "average man" "can run for 30 minutes without gasping for air" hahahaha good joke, game over Greglocock (talk) 03:39, 15 September 2014 (UTC)


 * I run for an hour, five times per week. For experience I know that the difficulty one experiences when carrying heavy stuff for more than just a short distance is more of a psychological issue, it's about accepting that it will be an exertion that you normally don't associate with the speed you are moving at. Count Iblis (talk) 03:50, 15 September 2014 (UTC)
 * I think you're missing what seems to be Greglocock's point. Regardless of whether it's true that someone who is "reasonably fit" and "can run for 30 minutes without gasping for air" can also carry their own weight for several km, this question wasn't about such people. It was about people the "average man" who probably can't do neither and isn't likely to be considered "reasonably fit". (Of course this will depend how you define "average" but even if you take the whole world and only include adults in a narrow age range. Even considering the large percentage of people in developing countries, it seems unlikely you're going to come up with the average being able to run for 30 minutes with gasping for air.) It may be worth considering under what conditions people can do so, but Greglocock's point remains. Nil Einne (talk) 13:52, 15 September 2014 (UTC)
 * Yes, I see this issue. Still, there is another issue here, and that is when you are not accustomed to doing this you will tend to walk too fast. So, regardless of fitness, there is a maximum speed that the fitness you have will allow you to move at and you will likely exceed that speed the less experience you have. Also the less fit you are the slower you have to move, which is then more likely to cause you to breach your maximum speed. You will then experience this as the load being too heavy while in reality it's caused by your brain not regulating the walking speed properly. Count Iblis (talk) 15:32, 15 September 2014 (UTC)


 * Not carrying, but on reaching a ~30° slope with a heavy wheeled load I started running. It is weird running fast(ish) and only managing inches with each step. Pushing at least as hard as slow running too. Was that also suboptimal? But since there was no ratchet, there's a constant backwards pushing force on you, and I have very weak leg muscles (for a man in his 20s). So maybe not. Is high rpm low mph a known method of training? Either increasing the time, weight and/or slope with gains in fitness or simply allowing the mph to go up and/or rpm to go down?


 * It's surprisingly hard to find information on this. The general rule for backpackers is that for sustained hiking, the pack weight should not exceed 30% of body weight, apparently for both men and women.  In this thread, a small woman asks whether she could plausibly carry 180 pounds in a fireman's carry, and the responses all indicate that it's possible with training.  How much a person can actually carry is heavily dependent on the shape of the object--very few people can lift a 180 pound box of steel, for example, because a fireman's carry would not be possible.  --Bowlhover (talk) 18:34, 15 September 2014 (UTC)


 * The test in 1914 for a UK Boy Scout (aged 11 to 18 years) to pass the Fireman's Badge included: "Fireman's lift carrying a boy his own size up and down twelve steps, or thirty yards on the level". This test was devised by one Captain Wells, a former Chief of the London Fire Brigade. A quick mental risk assessment suggests that present day Scouts won't be trying this out. Alansplodge (talk) 17:50, 17 September 2014 (UTC)
 * Actually, it may not have been so hard for the younger of those kids. Remember that when you halve someones height, but keep the rest of the body in propotion you make them eight times lighter.  The power from a muscle depends on it's cross-sectional area, which is only a quarter as much in a half-sized person.  So you'd have one quarter of the muscle power lifting one eighth of the weight - which is twice as easy as an adult who is trying to lift an adult.  11 year olds aren't half the height of an adult, but even if they are only a little bit shorter, you'd expect them to be much better able to pass this test. SteveBaker (talk) 20:54, 18 September 2014 (UTC)
 * Well maybe. Piggy back fights were a popular playground game at my school, until I ended up in hospital with a fractured skull as a result (perhaps it was the fighting element that was dangerous though). Alansplodge (talk) 20:36, 19 September 2014 (UTC)

ion.of Mo metal //9-15-14
How do I solve for the amount of mass (g) ionized by light...given only frequency of 1.09 x 10 15 /sec and 161 kJ of energy? — Preceding unsigned comment added by 2602:30A:C023:E6F0:A4BF:1382:BD46:EC06 (talk) 13:18, 15 September 2014 (UTC)
 * What is the full homework problem your teacher has asked you to solve? Throwing bits and pieces at us makes it hard for us to help you.  Instead, tell us the problem verbatim.  We won't solve it for you, but we can direct you to how to solve it yourself if you give us enough information.  -- Jayron  32  20:26, 15 September 2014 (UTC)
 * Without answering the question for the OP, photoelectric effect and work function are the relevant articles. Tevildo (talk) 23:17, 15 September 2014 (UTC)
 * One way to approach this is to work out how many photons at that frequency make up the given energy, with E=hν then calculate how many ions are made with that, (perhaps one ion per photon) then multiply the mass of one ion by the number to get the ending mass. The mass of an ion will not differ much from the atom, especially given the precision of your numbers. Graeme Bartlett (talk) 23:51, 15 September 2014 (UTC)