physics question

Originally posted by PBE6
I prefer to understand a problem well enough that I can derive the answer from first principles, so yes, if asked this question again (for the first time!) I would use the same approach but with the correct equation. I find that I learn much more this way - just look at this thread! Concision and clarity are the ultimate goal of course, but the detailed step-by-step solution can be an illuminating first draft.

I tend to agree with your position, your solution if far more fundamental, and a greater understanding can be exhausted from it, but unfortunately for me, a greater understanding must also be required to understand the grearter understanding!!..lol

thanks alot for all of your solutions

Originally posted by joe shmo
I tend to agree with your position, your solution if far more fundamental, and a greater understanding can be exhausted from it, but unfortunately for me, a greater understanding must also be required to understand the grearter understanding!!..lol

thanks alot for all of your solutions

Using ratios allows you to short cut the problem some of the time. Ratios have the first principles built into them already.

Think of it this way.

You have a result. You want a different result. So how much do you have to add or takeaway from your original result in order to get your preferred result? Adding or subtracting percentages will get you there some of the time.

But shortcuts don't always work so if you follow PB6's advice, you'll be a much smarter guy than I...mathwise. Cognitively though, i'll put the smack down every time.

😉

Originally posted by uzless
Using ratios allows you to short cut the problem some of the time. Ratios have the first principles built into them already.

Think of it this way.

You have a result. You want a different result. So how much do you have to add or takeaway from your original result in order to get your preferred result? Adding or subtracting percentages will get you ...[text shortened]... er guy than I...mathwise. Cognitively though, i'll put the smack down every time.

😉

So is the correct ratio 11/10 (1.1) or 10/9 (1.11...)?

Originally posted by Palynka
So is the correct ratio 11/10 (1.1) or 10/9 (1.11...)?

This is how we did it in grade 5 for a question like this.


On a full tank of gas, a car travelled 90% of the way to its destination. How much more gas does it need to reach its destination?

100%-90%=10%

Therefore, the car needs 10% more gas THAN IT STARTED WITH. Put another way, it's needs 100% of the difference between 90% and 100%.


EDIT:caps added just for palynka

Originally posted by uzless
This is how we did it in grade 5 for a question like this.


On a full tank of gas, a car travelled 90% of the way to its destination. How much more gas does it need to reach its destination?

100%-90%=10%

Therefore, the car needs 10% more gas.

I doubt you did that in grade 5, because it's wrong.

On a full tank of gas, a car travelled 50% of the way to its destination. How much more gas does it need to reach its destination?

100%-50%=50%

Therefore, the car needs 50% more gas.

Of course, that is wrong. The car needs 100% more gas. If a car travels 90% of the way to its destination with a full tank of gas, then it needs an extra 10/9-1 = 11,11...%

Originally posted by Palynka
I doubt you did that in grade 5, because it's wrong.

On a full tank of gas, a car travelled 50% of the way to its destination. How much more gas does it need to reach its destination?

100%-50%=50%

Therefore, the car needs 50% more gas.

Of course, that is wrong. The car needs 100% more gas. If a car travels 90% of the way to its destination with a full tank of gas, then it needs an extra 10/9-1 = 11,11...%

my god man. I thought it was obvious. I've re-stated the obvious for you.

Of course you needed the extra 10% more than you started with, not an extra 10 percent of what you have.

Next time, I will make sure I palynka-proof my answer.

Originally posted by uzless
my god man. I thought it was obvious. I've re-stated the obvious for you.

Of course you needed the extra 10% more than you started with, not an extra 10 percent of what you have.

Next time, I will make sure I palynka-proof my answer.

FAIL

Originally posted by uzless
my god man. I thought it was obvious. I've re-stated the obvious for you.

Of course you needed the extra 10% more than you started with, not an extra 10 percent of what you have.

Next time, I will make sure I palynka-proof my answer.

lol this doesn't even make sense... reread what you posted and think about it again.

Originally posted by uzless
my god man. I thought it was obvious. I've re-stated the obvious for you.

Of course you needed the extra 10% more than you started with, not an extra 10 percent of what you have.

Next time, I will make sure I palynka-proof my answer.

yeah...It definately needs 11.11.......% more fuel to complete it journey ( assuming the physical parameters of the trip do not vary at all)

Originally posted by Palynka
FAIL

The distance to target is 200 centimeters. Shot went 180cm.

In other words, 10% short. So, compress the spring an extra 10%.

10% of 1cm= 1.1cm.

Edit: (1cm + 10% of 1cm) = 1.1cm (just for palynka who can't follow skipped steps)

How's that. My original explanation. I'll leave it to you to figure out how to put it in words.

Originally posted by uzless
The distance to target is 200 centimeters. Shot went 180cm.

In other words, 10% short. So, compress the spring an extra 10%.

10% of 1cm= 1.1cm.

Edit: (1cm + 10% of 1cm) = 1.1cm (just for palynka who can't follow skipped steps)

How's that. My original explanation. I'll leave it to you to figure out how to put it in words.

FAIL

Again.

Normalize spring length to 200 and the initial compressed length to 100. Reveal Hidden Content

If a compression of 100 (normalization wlog) gives you a force of 180 then the spring constant is 1.8.

Then, to get a force of 200, you need to compress the spring to a length of 88.8... If you have compressed a length of a 100 and you need to compress an extra 11.11... units...then...

That's an extra 11,11...%.

Originally posted by Palynka
FAIL

Again.

Normalize spring length to 200 and the initial compressed length to 100. [hidden]or the math is too hard for uzless[/hidden]

If a compression of 100 (normalization wlog) gives you a force of 180 then the spring constant is 1.8.

Then, to get a force of 200, you need to compress the spring to a length of 88.8... If you have compressed ...[text shortened]... a 100 and you need to compress an extra 11.11... units...then...

That's an extra 11,11...%.

"compress the STRING an extra 10%"

I can't make it any clearer. My english skills only go so far.

Is PB6's 1.1 NOT the correct answer? (<--dam you pb6!!)

If it's not, then using a ratio would be like this.

180/1 = 200/X to give you 1.1111 as aramantine had. Either way, i'm a genious with mad math skillz 😴

Originally posted by uzless
"compress the STRING an extra 10%"

I can't make it any clearer. My english skills only go so far.

Is PB6's 1.1 NOT the correct answer?

If it's not, then using a ratio would be like this.

180/1 = 200/X to give you 1.1111 as aramantine had. Either way, i'm a genious with mad math skillz 😴

If you actually looked at PBE6 answer, you'd see that he doesn't get 1.1 exactly but by rounding the number.

Regarding the second point, so you finally agree that you were wrong and that you should NOT compress the spring by an extra 10% but by an extra 11.1(1)%?

Edit - Aramantine's answer coincides with my point, not yours.

Originally posted by Palynka
If you actually looked at PBE6 answer, you'd see that he doesn't get 1.1 exactly but by rounding the number.

Regarding the second point, so you finally agree that you were wrong and that you should NOT compress the spring by an extra 10% but by an extra 11.1(1)%?

Edit - Aramantine's answer coincides with my point, not yours.

ok guys...lets just settle this with an armwrestling match

Originally posted by joe shmo
ok guys...lets just settle this with an armwrestling match

Arm wrestling is for the ladies. Indian leg wrestling is where it's at!!!