# Elevation on Weight

Printable View

• Jul 20th 2008, 07:16 AM
magentarita
Elevation on Weight
If an object weighs m pounds at sea level, then its weight W (in pounds) at a height of h miles above sea level is given approximately by the function

W(h) = m[(4000)/(4000 + h)]^2

If Amy weighs 120 pounds at sea level, how much will she weigh on Pike's Peak, which is 14,110 feet above sea level?
• Jul 20th 2008, 07:26 AM
Simplicity
Quote:

Originally Posted by magentarita
If an object weighs m pounds at sea level, then its weight W (in pounds) at a height of h miles above sea level is given approximately by the function

W(h) = m[(4000)/(4000 + h)]^2

If Amy weighs 120 pounds at sea level, how much will she weigh on Pike's Peak, which is 14,110 feet above sea level?

For this question, you just have to substitute the value into the function after converting feet into miles.

$W(h) = m\left[\frac{4000}{4000 + h}\right]^2$

$1\text{ foot} = 0.000189393939\text{ miles} \implies 14100\text{ feet}\approx 2.67045455\text{ miles}$

Substituting this value (along with the weight in pound) into the function and it will give you weight on Pike's Peak. Round of your final answer to an appropriate significant figure.
• Jul 20th 2008, 07:48 AM
OnMyWayToBeAMathProffesor
reply
would the answer be $120\left[\frac{4000}{4000 + 2.67234848}\right]^2=119.9999464$?
• Jul 20th 2008, 07:59 AM
magentarita
Can I???
Can I round 2.67045455 to nearest unit and use it as the miles?

How about to the nearest tenths and use it as the miles?
• Jul 20th 2008, 09:14 AM
Simplicity
Quote:

Originally Posted by OnMyWayToBeAMathProffesor
would the answer be $120\left[\frac{4000}{4000 + 2.67234848}\right]^2=119.9999464$?

Yes, I get 120pounds when rounded to an integer value.

Quote:

Originally Posted by magentarita
Can I round 2.67045455 to nearest unit and use it as the miles?

How about to the nearest tenths and use it as the miles?

Yes, you can. For accuracy, it's best to keep it to as many significant figures but you can round the unit. You decide on the appropriate degree of accuracy. If the question asks you to give the final answer to 2dp then you should use the round the digit (of the unit to be put into the function) to 3dp (or 4dp for further accuracy).

EDIT: Personally, I would round to 3sf (2.67) and use this value as the the data provided for the question use integers hence the final answer should be given as an integer so for accuracy, 2dp unit of miles would be adequate.
• Jul 20th 2008, 12:35 PM
OnMyWayToBeAMathProffesor
Quote:

Yes, I get 120miles when rounded to an integer value.
'Air', don't you mean 120 pounds not miles?
• Jul 21st 2008, 04:44 AM
Simplicity
Quote:

Originally Posted by OnMyWayToBeAMathProffesor
'Air', don't you mean 120 pounds not miles?

Sorry, my bad. Yes, that is what I meant. I had 'miles' in my mind as that was my next topic of discussion so wrote that as opposed to 'pounds'. It corrected now, Thanks!
• Jul 27th 2008, 12:11 PM
magentarita
I thank all of you
It's great to have several replies to questions.