# Flying

• Oct 15th 2007, 10:49 AM
Memorex
Flying
hi all, i was thinking today about flying and jetpacks what not you get the idea long story short i need math help, lol

i weight 375lbs at most
so before i can even get off the ground i need 375lbs of thrust, but from there i need to be able to climb 50 feet into the air to avoid buildings etc can someone help me out i have no idea where to start on this one

do i work it out lb's per square inch or what, how do i calculate the amount of force needed to climb each foot anyone able to help me on this? also i need to be able to fly for about 2 hours max
• Oct 15th 2007, 12:48 PM
topsquark
Quote:

Originally Posted by Memorex
hi all, i was thinking today about flying and jetpacks what not you get the idea long story short i need math help, lol

i weight 375lbs at most
so before i can even get off the ground i need 375lbs of thrust, but from there i need to be able to climb 50 feet into the air to avoid buildings etc can someone help me out i have no idea where to start on this one

do i work it out lb's per square inch or what, how do i calculate the amount of force needed to climb each foot anyone able to help me on this? also i need to be able to fly for about 2 hours max

All you technically need is just a little bit of thrust more than your weight (plus the weight of the jetpack, of course.) If you want to get to a height of 50 ft before you are 90 years old, you will probably want a bit more thrust than that.

Answer this question to yourself: How much time do you want it to take to get to 50 ft? Then employ $\displaystyle y = \frac{1}{2}at^2$ to find the required acceleration, then $\displaystyle \sum F = ma$ to find the required thrust.

-Dan
• Oct 15th 2007, 12:53 PM
Memorex
Quote:

Originally Posted by topsquark

Answer this question to yourself: How much time do you want it to take to get to 50 ft? Then employ $\displaystyle y = \frac{1}{2}at^2$ to find the required acceleration, then $\displaystyle \sum F = ma$ to find the required thrust.

-Dan

thanks for the reply dan but theres one problem i don't understand any of those equasions at all sorry but its just gibberish to me i haven't done any form of math other then basic for the last 6 months the math part of my brain looks like a decayed fish, but i was thinking getting to 50ft in the space of a minute

(if you tell me how the equasions work i can do it from there )(like y = force or what ever)
• Oct 15th 2007, 03:04 PM
topsquark
Quote:

Originally Posted by topsquark
Answer this question to yourself: How much time do you want it to take to get to 50 ft? Then employ $\displaystyle y = \frac{1}{2}at^2$ to find the required acceleration, then $\displaystyle \sum F = ma$ to find the required thrust.

$\displaystyle \sum F = ma$

$\displaystyle T - w = ma$

$\displaystyle Tg - wg = mga$

$\displaystyle Tg - wg = wa$

$\displaystyle T = \frac{w(a - g)}{g}$
where T is your thrust, w is your weight, a is your acceleration, and $\displaystyle g = 32 ft/s^2$.

You wish to get to 50 ft. in a time t:
$\displaystyle y = \frac{1}{2}at^2$

$\displaystyle 50 = \frac{1}{2}at^2$

$\displaystyle a = \frac{2 \cdot 50}{t^2}$

$\displaystyle a = \frac{100}{t^2}$
where a is the acceleration and t is the desired time to reach 50 ft.

So plug in your desired time and you get a. Plug in a and the weight into your thrust equation and you'll get the thrust you need.

-Dan
• Oct 15th 2007, 03:07 PM
Memorex
wow that just made my migrain worse, add me on msn "stealthangel401@hotmail.com"