Physics Help - Why do weights help you fall faster?

[turnlow 0]

OK, I have had this conversation with a whuffo again without a satisfactory conclusion. Physics stars, please help.

What is the scientific explanation as to why wearing weights enables a jumps to fall fater? If I recall 8th grade physics correctly, objects should fall at the same rate, assuming equal resistence, regardless of weight. So how does adding weight help skydivers fall faster?

_________________________________________________

It matters not how strait the gate,
How charged with punishments the scroll,
I am the master of my fate:
I am the captain of my soul.

[Aviatrr 0]

Quote

OK, I have had this conversation with a whuffo again without a satisfactory conclusion. Physics stars, please help.

What is the scientific explanation as to why wearing weights enables a jumps to fall fater? If I recall 8th grade physics correctly, objects should fall at the same rate, assuming equal resistence, regardless of weight. So how does adding weight help skydivers fall faster?

_________________________________________________

That only applies in a vacuum(i.e. no air molecules to present resistance). Take two items, the same physical size(round items are best for illustrating this) - one much heavier than the other...drop them from the same height(the higher the better), and watch which one hits the ground first. An easy item to demonstrate this with is tennis balls. Cut a slit in one of 'em and drop as many pennies as you can in it. The two will be the same size, but vastly different weights.

Mike

[quade 3]

Apollo 15 Hammer and Feather demonstration.

Maybe you (or your friend) is (are) confused because you (he) heard, saw, remember something about this from high-school physics.

Fortunately for skydivers, it ONLY applies in a vacuum.
Air is a viscus medium that takes a certain amount of energy to push (or in this case pull) through. That energy is the weight of the object (both potential and kinetic).

A certain sized and shaped object it takes a certain amount of energy to pull its way through the medium. When the energy required to pull the object through the medium and the energy available are equal, the object will no longer accellerate. This is terminal velocity.

So, if two objects of the same size and shap are moving through the medium, but they have two different amount of energy available to them, then one will travel faster than the other.

quade -
The World's Most Boring Skydiver

[The111 0]

You've already received two good answers, but here is one more thing to chew on. Keep in mind that weight AND surface area both come into play determining how fast you fall through the atmosphere.

Quote

So how does adding weight help skydivers fall faster?

A similar question you could ask yourself to gauge your understanding... why does deploying a parachute slow you down from 120mph to almost nothing? You haven't added or removed any weight, have you?

www.WingsuitPhotos.com

[skydivingdutch 0]

Here is the real physics answer

An object falling through air with speed v eperiences a resistive force acting in the opposite direction, R
R = b*v , where b is a number tha depends on your coss section,whether or not you are wearing a wingsuit etc.

The total force on you is force gravity - R. The force determines your acceleration and hence your speed but the force also depends on the speed.
There is a speed where the resistive force exactly balances out the force of gravity, called terminal velocity, 120mph roughly for average skydiver.

With a greater mass, you influence the number b, making your resistive force, smaller, so that terminal velocity is a bit higher.
Also, RW is achieved by you controlling the value of b.

make sense?

http://dropman.com

[Fast 0]

Or here is a really long answer, that will help you explain even more.

Clicky!

There is even an explanation of skydiving, which is not to bad (though short)

~D
Where troubles melt like lemon drops Away above the chimney tops That's where you'll find me.
Swooping is taking one last poke at the bear before escaping it's cave - davelepka

[winsor 186]

Quote

Here is the real physics answer

An object falling through air with speed v eperiences a resistive force acting in the opposite direction, R
R = b*v , where b is a number tha depends on your coss section,whether or not you are wearing a wingsuit etc.

IIRC, that should be the square of the velocity.


Blue skies,

Winsor

[skydivingdutch 0]

nope, that is right. as i wrote we, obtain a differential equation

The kinetic engergy is proportional to an objects velocity squared.

http://dropman.com

[BoogieBob 0]

Here's the deal:

The drag force on a body moving through air (or any fluid) is expressed as:

F = 1/2 * (rho) * v^2 * Cd * S

Where:

F = drag force
(rho) = greek letter rho = fluid density
v = velocity of object (v^2 represents the square of the velocity)
Cd = coefficient of drag of body (varies with body shape NOT size)
S = Frontal area presented to airflow

Let's assume the same skydiver on the same day, then we can assume that (rho), Cd & S are constant (given incompressible flow, within which regime skydiving occurs). Let's define constant K to represent 1/2 * (rho) * Cd * S, we now have:

F = K * v^2

We know that:

F = m * a

where F = force, m = mass and a = acceleration.

So, the acceleration on the skydiver (in the vertical direction with an upward vector) is F / m, or:

a = K * v^2 / m

We also know that graviational acceleration is fairly constant (does not change appreciably, even at 13500 feet). Let's use 9.81 meters per second squared for this constant.

In stable freefall, the acceleration vectors are equal in magnitude and opposite in direction (acceleration due to drag has an upward vector while gravitational acceleration has a downward vector).

Thus, we obtain:

9.81 = K * v^2 / m

We are concerned about velocity here (and how mass affects it) so let's isolate v , yielding:

v = square root of (9.81 * m / K)

This equation shows the answer to your question. The stabilized freefall velocity IS affected by mass. In fact it varies as the square root of (m2 / m1). That is, the same skydiver with twice the mass will fall approximately 1.414 times faster.

[nathaniel 0]

Quote

That is, the same skydiver with twice the mass will fall approximately 1.414 times faster.

This result makes me think that weights do more than just add to a jumper's mass. I'll typically add no more than 10% of my bodyweight in additional weights...this gives me only an improvement of 4.8% in terminal velocity...110 mph becomes 115 mph.

I bet there's some aerodynamic benefit involved. I don't think it's just convenience that weights are worn on the belly and chest area.

nathaniel

My advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski?

[happythoughts 0]

Everything that I know about skydiving, I learned from cartoon animals. Every time that Wiley Coyote stepped off a cliff with that anchor... zoom. Without the anchor, he just paused for a second before falling.

Wearing chest weights will make you fall faster. However, using belly weights changes your presentation to the air. You are more chest-high. This handy for doing the mantis, it also spills more air.

[billvon 2,405]

>I'll typically add no more than 10% of my bodyweight in additional
>weights...this gives me only an improvement of 4.8% in terminal
>velocity...110 mph becomes 115 mph.

Weight alone doesn't change your speed; typically, it just allows you to fly at a given speed in a more relaxed body position. I've been on big ways where I've added just three pounds, and it made a difference between flying at my max fall rate and flying in a more relaxed position (read - better able to deal with sudden changes in fall rate.)

[Tonto 1]

Same surface area, more weight = faster.

Physics bullshit is all in a vacuum. We don't skydive in a vacuum.

Take 2 A4 pages. Crumple one into a ball. Drop both.
Which one goes faster?

t

It's the year of the Pig.

[JeffD 0]

or you could use the gravitational attraction of objects.

G=(m1*m2)/r^2

m1 is the mass of the earth. and m2 is the jumper mass. So if you increase the mass of the jumper, you increase the Gravitational attraction of the object or Force of the Earth on the object thus giving a higher terminal velocity because the Force of gravity is stronger(albeit a little).

[Squeak 17]

you tell him Tonto fuck all the fancy smancy talk

You are not now, nor will you ever be, good enough to not die in this sport (Sparky)
My Life ROCKS!
How's yours doing?

[Tonto 1]

I can't beleive all the people who graduated high school and don't know that we don't live in a fucking vacuum. Then when you've been your very own physics experiment for nearly 2 decades, someone will take out their calculator and start to argue....



t

It's the year of the Pig.

[jimmytavino 16]

.....

[Designer 0]

Flat out,weights are a "Pain in the arse".The other RW jumpers required me to were them(114 lbs,stickman).Here is the answer.Drop a feather and a bowling ball in a vacuum.Which will hit the ground first?Most people know that both will hit at the same time,because it,s in a vacuum.Well,we don,t freefall in a vacuum!Drag + wind resistance vary from jumper to jumper.I produce a buttload of drag with even a skin tight jumpsuit because I,m tall,very skinny and have much less mass than most other jumpers.Notice I said mass,not weight.To fix the problem,I must wear 16-20 lbs of lead shot.It,s a bigtime drag!So,I just freefly now!

[sssbc99 0]

Quote

It,s a bigtime drag!So,I just freefly now!

Good decision!

• Quote

[turnlow 0]

Thanks for the responses. I was looking for the specific formulas behind the logic and the answer now seems clear.

_________________________________________________

It matters not how strait the gate,
How charged with punishments the scroll,
I am the master of my fate:
I am the captain of my soul.

[billvon 2,405]

>I can't beleive all the people who graduated high school and don't
>know that we don't live in a fucking vacuum.

There are people who don't know how tides work, or what the air's made of, or why the sea is salty and rivers aren't. There are people who think we 'stick' to the surface of the planet because of its rotation, and people who think that an airliner's engines hold it up. None of that suprises me at all; it's depressingly common.

[geronimo 1]

Quote

OK, I have had this conversation with a whuffo again without a satisfactory conclusion. Physics stars, please help.

What is the scientific explanation as to why wearing weights enables a jumps to fall fater? If I recall 8th grade physics correctly, objects should fall at the same rate, assuming equal resistence, regardless of weight. So how does adding weight help skydivers fall faster?

_________________________________________________

Related article:
What determines Fall Rate?

.

---
I have a dream that my posts will one day will not be judged by the color of the fonts or settings in a Profile but by the content.
Geronimo_AT_http://ParachuteHistory.com

[kelpdiver 2]

Quote

or you could use the gravitational attraction of objects.

G=(m1*m2)/r^2

m1 is the mass of the earth. and m2 is the jumper mass. So if you increase the mass of the jumper, you increase the Gravitational attraction of the object or Force of the Earth on the object thus giving a higher terminal velocity because the Force of gravity is stronger(albeit a little).

Jeff, g is pretty much a constant on earth, so if you only look at this equation you're back to the feather and bowling ball falling together. The ball has a great gravitational force, but since a=f/m, it gets cancelled out. Only when the opposing force of drag is considered does the extra mass matter.

[NoShitThereIWas 0]

I haven't read everyone else's answers but the answer I am going with is Inertia. If I remember right from Physics, Inertia is an object's resistance to change. The greater the inertia of something, the less likely is to change; kind of like those sayings: Objects at rest remain at rest until moved by means of some outside force or objects in motion stay in motion in the same regard.

In skydiving the resistance we feel in freefall is due to the air restistance of air molecules colliding with the leading edge of our bodies which by nature is a kind of frictional force. The more weight we wear multiplied by our acceleration due to gravity, the greater our inertia and the greater our resistance to the opposing frictional force of air resistance while in freefall.

Roy Bacon: "Elvises, light your fires."

Sting: "Be yourself no matter what they say."

[Tonto 1]

Quote

There are people who don't know how tides work, or what the air's made of, or why the sea is salty and rivers aren't. There are people who think we 'stick' to the surface of the planet because of its rotation, and people who think that an airliner's engines hold it up. None of that suprises me at all; it's depressingly common.

And there are people who think I ride to work on a Zebra cos I live in Africa... And skydive off a giant kite... I don't think it should be common though, but I guess it is. That makes it tricky explaining how a good swoop works, eh?

t

It's the year of the Pig.