Tee's Knowledge Quiz

[Mister Tee]

This is a little quiz I put together a couple years ago to post on a couple of my sportbike boards. I think the intellect level here will be such that this will probably be a short thread, but let's see how good people are......

 

 

Here are a few questions to challenge those on their basic high school level scientific knowledge. You engineering types please try to let a few responses from the masses get in before you put your input in. Scenario: 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?

 

5A. What is your mass?

 

(Hint - the moon's gravitational pull is approximately 1/6th of earth's.)

[Joe Frickin' Friday]

You engineering types please try to let a few responses from the masses get in before you put your input in.

 

Apparently we are all engineer types here, since no one is chiming in. :confused:

 

This engineer will continue to abstain for the time being...

[ltljohn]

OK, I'll take a stab at it, high school was a long time ago.

 

This is a little quiz I put together a couple years ago to post on a couple of my sportbike boards. I think the intellect level here will be such that this will probably be a short thread, but let's see how good people are......

 

 

Here are a few questions to challenge those on their basic high school level scientific knowledge. You engineering types please try to let a few responses from the masses get in before you put your input in. Scenario: 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?

150 lbs

 

1B. What is your mass?

2187.5 troy oz ( you engineers do the math)

 

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

68.03 kg

 

2B. What is your mass?

68030g

 

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?

Balance scales because they are not effected by gravity I will know what something will weigh on earth relative to a known reference weight

 

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?

5440oz avdp

 

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

I weight the same as on earth because the weights on the other side of the balance are marked for earth gravity.

 

5B. What is your mass?

10.71 stone (British engineers do the math)

(Hint - the moon's gravitational pull is approximately 1/6th of earth's.)

[Albert]

I'm still trying to figure out how I got selected for the moon mission given my mass??

[ltljohn]

I'm still trying to figure out how I got selected for the moon mission given my mass??

 

They needed ballast for the space they are bringing moon rocks back in.

[Albert]

I'm still trying to figure out how I got selected for the moon mission given my mass??

 

They needed ballast for the space they are bringing moon rocks back in.

 

Don't worry, when they started talking about slugs I backed out (seems it was all a massive mistake).

[Mister Tee]

Hmmm, not quite ready to post the answers yet...

[Kathy R]

I'm still trying to figure out how I got selected for the moon mission given my mass??

 

 

So glad my mouth was not full of water at the moment I read this.

 

 

 

 

 

[Quinn]

I'm still trying to figure out how I got selected for the moon mission given my mass??

 

Don't worry, they'd just make two trips to take you.

 

 

[pbharvey]

I usually go to 9:15 mass, yeah that's my mass.

[Mister Tee]

I usually go to 9:15 mass, yeah that's my mass.

 

Alright, then calculate the WEIGHT that is removed from your shoulders...

[Mister Tee]

All right....

 

Here are my answers. If you want to read the original discussion, read it here: http://www.gsxr.com/showthread.php?t=48265

 

 

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

 

I weigh 190 lbs.

 

>1B. What is your mass?

 

My mass is 5.9 slugs, expressed in primary units. My mass could also correctly be reported as 190 lbm, but for reasons that will be discussed later, 190 lbm is not exactly equal to the weight unit of 190 lbf.

 

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

 

8.8 Newtons. But I had to calculate that. Metric scales are expressed in Kilograms, which is a mass.

 

>2B. What is your mass?

 

86 Kilograms.

 

>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?

 

Good question Tee. A doctor's balance scale (the thing with the sliding weights) measures MASS ONLY, and not weight. So on the moon, any other planet, or even in a vertical acceleration, the scale will read the same. Now, on the other hand, a spring loaded bathroom scale is opposite, and it measures WEIGHT ONLY, and not mass. That scale, when used on the moon, will correctly report your weight as 1/6th of what it would be on the earth.

 

As a side note, U.S. customary balance scales that read pounds are actually calibrated to read pound-mass (lbm), which by definition is 1 slug/32.2. Since the actual gravitational acceleration is 31.some odd and variable number, your reported mass in lbm will be slightly different than your weight in lbf, although in reality the difference will be less than the accuracy of the scales so we usually don't worry about it.

 

>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?

 

Okay, okay. That question was intended to confuse the "C" students. A "C" student would have assumed that 32.2 and/or 9.8 was 1 G and that the weight would be 340 lbs (170 x 2 total gravities.) The "B" student would have assumed that the Tee screwed up his units, and meant to report "feet/sec/sec" (an acceleration) and not "feet/sec" (a speed) and would have said 340 lbs. The "A" student would have recognized by the phrase "constant climb rate" that there is in fact no acceleration, and no corresponding change in weight. That's the correct answer.

 

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

 

As discussed before, your doctor's balance scale will report the same "weight" that it would on the earth, because a balance scale can only measure a mass. You would have to calculate your actual weight if you wanted it.

 

>5A. What is your mass?

 

It's whatever the balance scale reported it as. Again, if you used a spring bathroom scale, your weight would be reported as 1/6th of the value it would read on earth and you would have to calculate your mass.

[Albert]

My head hurts. Can I go out and play now?

[Chad F.]

Wow, don't read this one first thing in the morning, I'm done for the whole day now.

[Quinn]

I'm still trying to figure out how many cubits are in a farthing.

 

 

[artig]

>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?

 

Okay, okay. That question was intended to confuse the "C" students. A "C" student would have assumed that 32.2 and/or 9.8 was 1 G and that the weight would be 340 lbs (170 x 2 total gravities.) The "B" student would have assumed that the Tee screwed up his units, and meant to report "feet/sec/sec" (an acceleration) and not "feet/sec" (a speed) and would have said 340 lbs. The "A" student would have recognized by the phrase "constant climb rate" that there is in fact no acceleration, and no corresponding change in weight. That's the correct answer.

 

OK, it's a long time ago, but I was taught that g varies with distance from the centre of the earth. It does not have the same value on the top of Mt Everest as it does in Death Valley. As the plane climbs at a constant rate your weight should decrease with altitude. The bathroom scales, however, may not be accurate enough to measure the change. Unless you hit turbulence, in which case it's anyone's guess how much you weigh at any one instant. And you'd probably be asked to leave the lavatory.

 

[artig]

By the way, there's an interesting map of variations in the earth's gravity at this APOD page.

[Mister Tee]

OK, it's a long time ago, but I was taught that g varies with distance from the centre of the earth. It does not have the same value on the top of Mt Everest as it does in Death Valley. As the plane climbs at a constant rate your weight should decrease with altitude. The bathroom scales, however, may not be accurate enough to measure the change. Unless you hit turbulence, in which case it's anyone's guess how much you weigh at any one instant. And you'd probably be asked to leave the lavatory.

 

Interesting you would bring up that point. In fact, the body inteprets "G" forces exactly the same as it interprets gravity, so, if you were in an airplane, and you were flying completely blind, the only "down" sense you have is whatever is pushing up against your ass. You can be completely upside down and think you're still upright. Too many (unqualified and unequipped) pilots have been killed flying in to clouds, not realizing this.

 

EDIT: Secondary point - the fact that gravitational pull is variable based on altitude, as well as geographic position, is one reason why neither SI or US Customary units define base units on gravitational acceleration.