FAQ Memberlist Usergroups Register Log in
Profile Log in to check your private messages Search

Homework help....2.0
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
 
Post new topic   Reply to topic     Forum Index -> General Discussion
Author Message
Nem



Joined: 14 Apr 2008
Posts: 2141
Location: England

PostPosted: Wed Feb 08, 2012 8:00 pm    Post subject: Reply with quote

I'm doing some quick sums to try and work out how much energy someone spends in their workout and I think I must have made a mistake somewhere.

U=mgh

Wherein:

U = energy spent in joules
m = mass in kg
g = 9.81
h = around .5 meters

45*9.81*0.5 = 220.725

Or, with one calorie being around 4.185 joules, around 52 calories for a single rep.

Which just seems like it must be wrong. If that were the case no-one would ever need to worry about weight. They'd just lift 45kg 20 or 30 times a day and burn off a thousand or so calories.

So something must be wrong with my working out. But I'm not sure what.

Edit: Or something's wrong with my vision of people, I guess that works too. I just find it hard to believe the person's lied about their diet. Doesn't seem to be any percentage in it for them. Bleh.

Edit2: Or I just vastly underestimate the amount of calories in foods I suppose. :/

Edit3: Possibly I'm about by around a 1000, calories possibly actually K calories when reported in foodstuffs?

Edit4: After some digging this does seem to be the case. Thought we now have the alternate problem of explaining how exercise of that type ever helps anyone. Wink But that does fit in better with the observations about the person in question so. -shrug- Yay, happy conclusion, sort of. ^_^

Edit5: Still looks iffy. Wonder how efficient people are at converting the energy they get into work?
_________________
Never forget,
We stroll along the roof of hell
Gazing at flowers.
- Issa
Back to top
View user's profile Send private message MSN Messenger
Tenshi



Joined: 18 Apr 2008
Posts: 2594
Location: Star Stuff

PostPosted: Thu Feb 09, 2012 8:39 pm    Post subject: Reply with quote

At a glance, I think that you've missed a conversion from kilograms into grams (so a division by 1000). I'd like to know a bit more about your units, though.

M = Mass in kg (1000*weight-in-grams)
G = ?
H = ?

Also, depending on the rep, you're not actually moving the full body weight of the individual, are you?
_________________
. Dubbed "Usagi" by AsA .
Keeper of the Siderean Swords

"If by chance some day you're not feeling well, and you should remember some silly thing I've said or done, and it brings back a smile to your face or a chuckle to your heart, then my purpose as your clown has been fulfilled."
Red Skelton
Back to top
View user's profile Send private message AIM Address
Nem



Joined: 14 Apr 2008
Posts: 2141
Location: England

PostPosted: Thu Feb 09, 2012 10:17 pm    Post subject: Reply with quote

g= roughly acceleration due to gravity (gravitational constant seems to be something different Razz ) in m/s or ~9.81somethingsomething, I believe.
h= height thing lifted to in metres - sticking 0 as the floor/starting position.

You're lifting a 45kg weight.

^_^
_________________
Never forget,
We stroll along the roof of hell
Gazing at flowers.
- Issa
Back to top
View user's profile Send private message MSN Messenger
Tenshi



Joined: 18 Apr 2008
Posts: 2594
Location: Star Stuff

PostPosted: Thu Feb 09, 2012 11:51 pm    Post subject: Reply with quote

Hm. I've never calculated this before, but wouldn't it be better to calculate Force (in joules), and then calculate the calories required to generate that level of force?

From Wiki:
Code:
http://en.wikipedia.org/wiki/Newton's_laws_of_motion#Impulse


But I haven't taken calculus, so I don't know how to work the formula.

Basically, once you convert the force into joules, you can calculate the number of joules generated by burning X number of calories. From a simple Google search, this is actually an obscenely complicated calculation, so I'm afraid you'll either need to trust one of the calculations listed on the web or ask someone with a bit more skill at this.

Ah! Did some research. Trusting myself to be able to work the math is ridiculous when there's a wonderful resource such as vastly oversaturated health markets on the ol' interweb.

According to this handy website...
Code:
http://www.livestrong.com/article/185358-how-to-determine-calories-burned/

You're looking at the equation of..
Code:
[(heart rate x 0.6309) -- (weight x 0.09036) + (age x 0.2017) -- 55.0969] x time / 4.184


That sort of bypasses force, joules, and everything, doesn't it? The equation for women is different - it's on that web site. That's the one specifically geared toward men. I have no idea what it's for, but it's probably a decent baseline useful for checking the other calculation..

Sorry I can't be more help. It was a good diversion, though! Thank you for that. Good to get my mind around something not involved in non-academic pursuits.
_________________
. Dubbed "Usagi" by AsA .
Keeper of the Siderean Swords

"If by chance some day you're not feeling well, and you should remember some silly thing I've said or done, and it brings back a smile to your face or a chuckle to your heart, then my purpose as your clown has been fulfilled."
Red Skelton
Back to top
View user's profile Send private message AIM Address
Tamir



Joined: 22 Mar 2008
Posts: 1629
Location: Israel

PostPosted: Fri Feb 10, 2012 8:24 am    Post subject: Reply with quote

Okay, not to be mean or anything, but you guys are kind of off. Measuring force in joules? Nem's calculation not taking into account at all the energy required to keep the weight in the air or to bring it down? At least you noticed to Kcal mistake.

Calculating this sort of thing is generally very difficult, and requires lots of extra information such as how you're lifting the weight (over you? next to you?), how quickly you're lifting it, and such.
Back to top
View user's profile Send private message
Nem



Joined: 14 Apr 2008
Posts: 2141
Location: England

PostPosted: Sun Feb 12, 2012 11:52 am    Post subject: Reply with quote

Oh Tam ^_^ if I cared about being told I was right, I'd just find the nearest moron and beat them over the head with rhetoric until they agreed with me. You go right on being 'mean' Wink

If the potential energy in joules is given by U=mgh, and g is given in ms, can I just substitute t in seconds for h, for the holding it in the air bit?

But then I'm not putting energy into something when it's just sitting on a desk - it's not becoming more energetic while it stays there. So where does the energy we're spending keeping it in the air go if it doesn't go into the object? :/

Take it down - I suppose I could subtract the rate of descent from 9.8... etcetc to get the energy required?

---

I believe the person was lifting it over them - with them lying on their back on one of those bench thingumies.

@Tenshi - that is a rather clever way of guestimating it. ^_^

I think calculus was about relating one graph to another. There was an A Level class doing it on the board when I was waiting for a lesson once. So presumably you just divide whatever's on one axis by the other. Don't know though - stopped doing maths after it ceased to be compulsory =p Too much boring textbook: Here's a formula, here are a number of exercises where you will apply the formula.... Here's the next formula.... @_@ zZZ =p

No idea what the hugely elongated S would be for though ^^;
_________________
Never forget,
We stroll along the roof of hell
Gazing at flowers.
- Issa
Back to top
View user's profile Send private message MSN Messenger
Tamir



Joined: 22 Mar 2008
Posts: 1629
Location: Israel

PostPosted: Mon Feb 13, 2012 5:59 pm    Post subject: Reply with quote

Okay, I'm going to start with noting that I don't know how to solve this problem in a satisfactory way myself, this despite having a degree in physics. >_> I don't know how to properly take into account arm shape and musculature. It doesn't tend to work like classic physics where you have solid blocks of stuff with no inner structure.

Nem wrote:
If the potential energy in joules is given by U=mgh, and g is given in ms, can I just substitute t in seconds for h, for the holding it in the air bit?

Short answer: No. Longer answer: No way.
I can appreciate why you'd want to include time in that equation, since it's missing, but you can't just do that. Potential energy is time-independent. What you're trying to calculate here is work, which can change over time, but you're using the wrong equation to do so.

Nem wrote:
But then I'm not putting energy into something when it's just sitting on a desk - it's not becoming more energetic while it stays there. So where does the energy we're spending keeping it in the air go if it doesn't go into the object? :/

The object isn't becoming more energetic, but you're definitely expending energy (and I'm sure you don't need me to tell you that). The "missing" energy is mostly going into heat and chemical bonds.

Nem wrote:
Take it down - I suppose I could subtract the rate of descent from 9.8... etcetc to get the energy required?

Uh, I don't really understand where you're going with that. But in general, the method is flawed. Potential energy isn't the only player in this game.

Nem wrote:
I think calculus was about relating one graph to another. There was an A Level class doing it on the board when I was waiting for a lesson once. So presumably you just divide whatever's on one axis by the other.

Calculus is about studying the rate of change of functions and their properties. Sort of. It's hard to sum up in a few words.

Nem wrote:
No idea what the hugely elongated S would be for though ^^;

That would be integration. =) Which would be the opposite of differentiation, which is finding the rate of change of a function.
Back to top
View user's profile Send private message
Asa



Joined: 10 Apr 2008
Posts: 3538
Location: Grammar Police HQ. Watch your language, I'm armed with the NYTimes Style Book AND Strunk and White!

PostPosted: Wed Mar 28, 2012 1:15 pm    Post subject: Reply with quote

Okay, peeps, another "How do I cite..." question.

I think I stumbled across an internal report from AT&T - it's attributed to people at AT&T Labs - Research, not a publication. How do I cite that?
_________________
Self-styled Forum Grandmother, because I hand out nicknames and hugs whether you want them or not. ^_^

Keeper of the Library and the Gateway to Haven

Nem: "It's the sort of face you just know is getting ready to poke you with something sharp."
BS: "...then insist you eat a brownie."
__________________
If we shadows have offended,
Think but this and all is mended...
Give me your hands if we be friends,
And Robin shall restore amends.
Back to top
View user's profile Send private message Visit poster's website
Allicat



Joined: 14 Apr 2008
Posts: 1390
Location: Back in the Shire.

PostPosted: Wed Mar 28, 2012 1:49 pm    Post subject: Reply with quote

An interesting one. Unpublished material often doesn't have the information required for a full reference. Where did you find it? If it was on the internet, it might be best to reference it as a webpage.

Author surname, Initials. Copyright date*. Title of page. Company name. Available from [page url]. Accessed [current date].

* (should be at the bottom of the page or on a 'legal' or 'security' page)

Hope this is some help!
_________________
He who does not eat cheese will go mad. ~ French proverb.

Keeper of the fallen leaves. 'Cos they're still pretty.
Back to top
View user's profile Send private message
Asa



Joined: 10 Apr 2008
Posts: 3538
Location: Grammar Police HQ. Watch your language, I'm armed with the NYTimes Style Book AND Strunk and White!

PostPosted: Wed Mar 28, 2012 5:05 pm    Post subject: Reply with quote

That is a help, and I hadn't considered it. I put it in the system as a "report" since that seemed closest. What do you think about that option?
_________________
Self-styled Forum Grandmother, because I hand out nicknames and hugs whether you want them or not. ^_^

Keeper of the Library and the Gateway to Haven

Nem: "It's the sort of face you just know is getting ready to poke you with something sharp."
BS: "...then insist you eat a brownie."
__________________
If we shadows have offended,
Think but this and all is mended...
Give me your hands if we be friends,
And Robin shall restore amends.
Back to top
View user's profile Send private message Visit poster's website
Tenshi



Joined: 18 Apr 2008
Posts: 2594
Location: Star Stuff

PostPosted: Wed Mar 28, 2012 6:35 pm    Post subject: Reply with quote

Perhaps most importantly, what citation style are you using? MLA, APA, something else..?

I'd recommend citing it as a web page, actually. If you've drawn it from the web, then standard rule (from the competitive writing thing I entered) is to cite it as a web page. The exception is if it's a PDF of another item, which is its own unique citation.
_________________
. Dubbed "Usagi" by AsA .
Keeper of the Siderean Swords

"If by chance some day you're not feeling well, and you should remember some silly thing I've said or done, and it brings back a smile to your face or a chuckle to your heart, then my purpose as your clown has been fulfilled."
Red Skelton


Last edited by Tenshi on Wed Mar 28, 2012 11:46 pm; edited 1 time in total
Back to top
View user's profile Send private message AIM Address
Allicat



Joined: 14 Apr 2008
Posts: 1390
Location: Back in the Shire.

PostPosted: Wed Mar 28, 2012 7:42 pm    Post subject: Reply with quote

If citation style is unclear I tend to stick with the Harvard system but if in doubt just put in all the details you have in the format you've been given. If no format, just keep it uniform with the rest of your document.
_________________
He who does not eat cheese will go mad. ~ French proverb.

Keeper of the fallen leaves. 'Cos they're still pretty.
Back to top
View user's profile Send private message
Tinu.



Joined: 23 Mar 2008
Posts: 3690
Location: The land of dreams

PostPosted: Wed Mar 28, 2012 8:55 pm    Post subject: Reply with quote

You could cite it as a webpage, but you can also cite it as a letter. All of that information should be available if it's a proper report. If it's not, then just do a webpage.

If you really want to know for certain, I have my Business writing class tomorrow morning and I'll ask my professor for you.
Back to top
View user's profile Send private message
Asa



Joined: 10 Apr 2008
Posts: 3538
Location: Grammar Police HQ. Watch your language, I'm armed with the NYTimes Style Book AND Strunk and White!

PostPosted: Thu Mar 29, 2012 6:09 am    Post subject: Reply with quote

It's a PDF of a thirty-page report linked from the AT&T Research website. It's located under the private folders of the respective authors. Citing it as a report seems to give enough information, so that's what I think I'll go with.

I was taught that the standard for Linguistics papers (at least at my alma mater) is APA, so that's what I use.
_________________
Self-styled Forum Grandmother, because I hand out nicknames and hugs whether you want them or not. ^_^

Keeper of the Library and the Gateway to Haven

Nem: "It's the sort of face you just know is getting ready to poke you with something sharp."
BS: "...then insist you eat a brownie."
__________________
If we shadows have offended,
Think but this and all is mended...
Give me your hands if we be friends,
And Robin shall restore amends.
Back to top
View user's profile Send private message Visit poster's website
Asa



Joined: 10 Apr 2008
Posts: 3538
Location: Grammar Police HQ. Watch your language, I'm armed with the NYTimes Style Book AND Strunk and White!

PostPosted: Tue Jul 31, 2012 3:41 pm    Post subject: Reply with quote

Is there a quick way to find the range of a column of numbers in Excel? I have 95 columns of 158 rows each, and I'd rather not type out the whole formula by hand 95 times...

Thanks!
_________________
Self-styled Forum Grandmother, because I hand out nicknames and hugs whether you want them or not. ^_^

Keeper of the Library and the Gateway to Haven

Nem: "It's the sort of face you just know is getting ready to poke you with something sharp."
BS: "...then insist you eat a brownie."
__________________
If we shadows have offended,
Think but this and all is mended...
Give me your hands if we be friends,
And Robin shall restore amends.
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic     Forum Index -> General Discussion All times are GMT - 4 Hours
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Page 8 of 9

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



Elveron phpBB theme/template by Ulf Frisk and Michael Schaeffer
Copyright Ulf Frisk, Michael Schaeffer 2004


Powered by phpBB © 2001, 2002 phpBB Group