# How much lbf is required to lift 300lbs

## Main Question or Discussion Point

15inches above ground ; hovering, stabilizing system is assumed in the system.

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How quickly does it need to travel those 15 inches?

russ_watters
Mentor
That aside, the minimum required is a hair over 300 lb.

to make it hover at a rate , right at 10-20inches,

mheslep
Gold Member
0 lb in free fall on, say, the space station. ~50lb on the Moon. :tongue:

I see, So I have a Ball which is 6ft high 6ft in width and weights 400lbs,; you're saying it requires 300lbf to maintain a height of 15 inches above a flat surface(ground)

mheslep
Gold Member
No, 400lbs if the ball weighs 400lbs (on earth). Height is not relevant.

I see, umm analogy 1, a chair in a form of a 75 % of sphere or circle or a pie(pizza 12 slices) with 4 slices taken out. weights 400lbs , 3 engines 1 in middle 2 on side for stabilizing 10-20 inches above a flat surface. you saying it requires 400lbs of thrust for that?

The amount of force it requires is the same amount that it weighs. So the shape, size, material, color, bling or religious significance is irrelevant...if it weighs 400lbs then it will require 400lbs of force. If it weighs 47901.87lbs, then it will require 47901.87lbs of force to keep it hovering.

Do you really have a degree in Aeronautical Engineering?

How quickly does it need to travel those 15 inches?
You have a good designer's mind

I see, umm analogy 1, a chair in a form of a 75 % of sphere or circle or a pie(pizza 12 slices) with 4 slices taken out. weights 400lbs , 3 engines 1 in middle 2 on side for stabilizing 10-20 inches above a flat surface. you saying it requires 400lbs of thrust for that?
A jet engined pizza chair that weighs 400lbs? Kay.

To hover it will need 400lbs thrust. To raise it you need to overcome gravity, any thrust that exceeds the force due to gravity will keep raising it. As fuel is used it will gradually require less thrust to hold it in the same place because it weighs less.

The amount of force it requires is the same amount that it weighs. So the shape, size, material, color, bling or religious significance is irrelevant...if it weighs 400lbs then it will require 400lbs of force. If it weighs 47901.87lbs, then it will require 47901.87lbs of force to keep it hovering.

Do you really have a degree in Aeronautical Engineering?
I Understand it requires the same amount of thrust;weight to counter gravity But you did not read what I asked properly... I said 10-20inches above ground. I do not have a degree in Aeronautical Engineering but I will ;

Last edited:
Redbelly98
Staff Emeritus
Homework Helper
I Understand it requires the same amount of thrust;weight to counter gravity But you did not read what I asked properly... I said 10-20inches above ground. I do not have a degree in Aeronautical Engineering but I will ;
Have you taken freshman physics? That is pretty much the level of understanding needed here. If the object is to be floating in place, then it is not accelerating, therefore the net force is zero -- no matter how high off the ground it is.

Oh I see , it never hurts to know too much, thanks now I need to design a stabilizing system for the pizza chair

Yea, if you have 400lbf of lift, you will be gravity-neutral. If you need to get it off the ground you need more than the 400lbf. How much more is determined by how fast you want to lift it. How fast you want to lift it will also affect how long you apply the extra force required, which will then determine how much of an overshoot you will see. (For example, you use 1000lbf of lift and shoot upward, you reduce the lift to 400lbf at 15in, but you will continue upward somewhat.

That being said. 401 lbf will give you net postive lift. But you sure as heck wont be breaking any speed records.

Well thank you fellows :D All of you guys input was worth reading 10folds