Tee's Knowledge Quiz - Sportbike Forum: Sportbike Motorcycle Forums
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 26 (permalink) Old 01-03-2008, 08:52 AM Thread Starter
Registered User
 
Join Date: Jan 2007
Location: Sacramento, CA USA 96814
Posts: 369
Tee's Knowledge Quiz

I came up with a short quiz and posted this on another board. I just wanted to see how savvy folks were around here. I'll post the answers later if I need.

Here are a few questions to challenge those on their basic high school level scientific knowledge. Scenario: With all that heavy holiday eating, you're concerned about your health, and you're preoccupied with your weight, so you monitor it every chance you get.

1A. You step on a set of scales marked in U.S. customary units. What is your weight?

1B. What is your mass?

2A. You step on a set of scales marked in SI (metric) units. What is your weight?

2B. What is your mass?

3. You have been selected to crew on the moon station for a month. Your doctor lends you his balance scales, and you have a set of spring loaded bathroom scales as well. Mission control says you can take one scale but not both. Which one do you take, and why?

4. On the flight to Houston, you step on the bathroom scales in the lavatory of your 747 while it is on the ground. Your weight is 170 lbs. After you take off, the Captain informs you that the plane has attained a constant climb rate of 1932 feet per minute (that's 32.2 feet per second, or 9.8 meters per second, for you metric people. We're keeping the numbers simple here). You step on the scales again - what do they read?

5A. You get to the moon. You pull out your doctor's balance scale and weigh yourself. What is your weight?

5B. What is your mass?

(Hint - the moon's gravitational pull is approximately 1/6th of earth's.)
Mister Tee is offline  
Sponsored Links
Advertisement
 
post #2 of 26 (permalink) Old 01-03-2008, 09:41 AM
Registered User
 
mkeeney's Avatar
 
Join Date: Aug 2003
Location: Rome, GA
Posts: 659
Re: Tee's Knowledge Quiz

Don't read any answers until you post your own.










1A. You step on a set of scales marked in U.S. customary units. What is your weight?

205 lb

1B. What is your mass?

6.36 slugs

2A. You step on a set of scales marked in SI (metric) units. What is your weight?

Probably reads 93 kg, but should read 913 N

2B. What is your mass?

93 kg

3. You have been selected to crew on the moon station for a month. Your doctor lends you his balance scales, and you have a set of spring loaded bathroom scales as well. Mission control says you can take one scale but not both. Which one do you take, and why?

The answer you're looking for is balance scales because they will read the same regardless of gravity. I would take the bathroom scales though because they are much more portable, and I can divide by 6.

4. On the flight to Houston, you step on the bathroom scales in the lavatory of your 747 while it is on the ground. Your weight is 170 lbs. After you take off, the Captain informs you that the plane has attained a constant climb rate of 1932 feet per minute (that's 32.2 feet per second, or 9.8 meters per second, for you metric people. We're keeping the numbers simple here). You step on the scales again - what do they read?

170 lbs. - almost got me.

5A. You get to the moon. You pull out your doctor's balance scale and weigh yourself. What is your weight?

170 lbs.

5B. What is your mass?

5.3 slugs

-
"We didn't trade shoves; I did all the shoving." -Bobby Knight, 1981
mkeeney is offline  
post #3 of 26 (permalink) Old 01-03-2008, 09:45 AM
 
Join Date: Mar 2004
Posts: 8,798
Welcome to highscool physics.


1a. 170lbs
1b. No idea what the english unit of mass is, but i think its still pounds, or maybe troy pounds, or some other rediculous unit.
2a. some large number of newtons
2b. about 80kg
3. I'm going to be a smartass. I'm going to take the spring scales and a calculator, to convert in lesser gravity. It costs something like $20k to bring a pound into orbit, and I dont feel like ripping off the taxpayer just so that I can have my balance scales
4. 340lbs at 2g's. Not that I would ever get that far because the planes wings would rip off long before that. its a 747 for farks sake
5a. still 170lbs, balance scales dont care what the gravity is, as long as there is one.
5b. still around 80kg

Wtf is the hint for? I suspect you ment to ask the question with spring scales, or you are just trying to confuse people.


Edit: crap, got me with the plane...




Last edited by Vash; 01-03-2008 at 09:50 AM.
Vash is offline  
 
post #4 of 26 (permalink) Old 01-03-2008, 10:10 AM
 
Join Date: Jun 2001
Posts: 1,992
Arrgghh. The plane one got me too.
Kevlar7R is offline  
post #5 of 26 (permalink) Old 01-03-2008, 10:12 AM Thread Starter
Registered User
 
Join Date: Jan 2007
Location: Sacramento, CA USA 96814
Posts: 369
Heh, heh, heh. Good, good.

FYI a 747 has an operational load factor limitation of 2.5 g's. New aircraft, including heavy airliners, are certified for a minimum load factor of 3.8 g's in the normal category.
Mister Tee is offline  
post #6 of 26 (permalink) Old 01-03-2008, 10:16 AM
 
Join Date: Mar 2004
Posts: 8,798
Really? Damn, that would be pretty damn frightening.



Vash is offline  
post #7 of 26 (permalink) Old 01-03-2008, 10:20 AM Thread Starter
Registered User
 
Join Date: Jan 2007
Location: Sacramento, CA USA 96814
Posts: 369
Not really. A constant 60 degree bank is 2.5 g's. In fact, Airbus flight computers limit the maximum bank angle of 60 degrees just so that limit isn't exceeded. And it's very easy to exceed 2 g's in moderate turbulence.
Mister Tee is offline  
post #8 of 26 (permalink) Old 01-03-2008, 10:29 AM
 
Join Date: Mar 2004
Posts: 8,798
Learn something new every day...

Here is my favorite question to make smart people feel stupid (best used verbally)

Whats two plus two devided by two?



Vash is offline  
post #9 of 26 (permalink) Old 01-03-2008, 10:34 AM
 
Join Date: Jun 2001
Posts: 1,992
Quote:
Originally posted by Vash
Learn something new every day...

Here is my favorite question to make smart people feel stupid (best used verbally)

Whats two plus two devided by two?
3. Order of operations gets em.

2+ (2/2)=3
2+ (1)=3
Kevlar7R is offline  
post #10 of 26 (permalink) Old 01-03-2008, 10:45 AM Thread Starter
Registered User
 
Join Date: Jan 2007
Location: Sacramento, CA USA 96814
Posts: 369
2?

As a side note, the secondary English unit of mass is the pound-mass (lbm), which, by definition is 1 slug/32.2. This is so one lbm will numerically approximately equal one pound-force (lbf, primary weight unit) when placed on a scale. And in fact, most balance scales that display pounds actually are calibrated in lbm, which is a mass. (Since the actual acceleration due to gravity is 31.some odd and variable number feet/sec/sec, 1 lbm doesn't exactly weigh 1 lbf. The difference is less than the accuracy of a normal balance or scale so we don't worry about it.)

Also, and this really screws with people when doing complex thermodynamic calculations between the units, but in the metric system, mass (grams) is a base unit, and weight (newtons) is a derived unit, calculated from mass. In the English system, it's opposite - weight (lbf) is a base unit, and mass (the slug) is a derived unit. A slug, by definition, is the mass that will incur a force of 1 lbf when subjected to an acceleration of 1 ft/sec/sec. Likewise, a Newton is the force incurred when 1 kg is subjected to an acceleration of 1 m/sec/sec. Note that neither system uses gravity in the definition of either force or mass.

(EDIT: I think I received payback)
Mister Tee is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Sportbike Forum: Sportbike Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome