physics question / skydiving weight

SixPapaCharlie

SixPapaCharlie

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Let's say you have a weight. Something nonspecific, hanging from a rope.
This generic "thing" weighs 100 lbs.
Half way between the widget and top of the rope is a scale showing the unknown, undefined item at the end of the rope does in fact weigh 100 lbs.


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Now let's put a parachute the top of the rope and drop it.
While falling, what will the scale say with regard to the undefined weight the end during the fall?




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Sir Issac is spinning...
 
When you pushover for descent what do you feel in the seat of your pants? What do you feel when you are in a steady 500 fpm descent?
 
Does "while falling" mean the parachute is deployed or is the whole thing just falling until it opens?

A free body diagram shouldn't be too difficult if I can understand what you're asking :yes:

Forces downwards - gravity
Forces upwards - air resistance (parachute/objects), friction

As it fell without the chute open, the scale would read close to 0 as it flailed about while dropping at the same speed as the object.

During opening of the chute, the scale would read a lot higher than 100lb due to the sudden deceleration.

If the parachute is stable and falling at a certain rate, there would be no acceleration - except for gravity. That'd be your 100lb reading on the scale (minus a little for the wind pushing up on the scale but it's negligible).

Imagine someone hanging off of you while hang gliding :D you are the scale.
 
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Ok so it would pull the same on the scales because the objects are still relative to one another and doesn't matter that they are falling
 
Would it be different if using the metric system
 
I vote less that 100 lbs while suspended under the parachute. The 'object' is still descending so you still have the gravity minus the air resistance equation. The variable is the size of the parachute since a smaller parachute will descend at a faster rate than a larger parachute given an equal weight 'object' suspended under it.
 
JCranford said:
I vote less that 100 lbs while suspended under the parachute. The 'object' is still descending so you still have the gravity minus the air resistance equation. The variable is the size of the parachute since a smaller parachute will descend at a faster rate than a larger parachute given an equal weight 'object' suspended under it.
Click to expand...

You're assuming the scale has no air resistance?
 
SixPapaCharlie said:
Ok so it would pull the same on the scales because the objects are still relative to one another and doesn't matter that they are falling
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Sir Issac's rpm has dropped considerably
 
overdrive148 said:
During opening of the chute, it'd read a lot higher than 100lb due to the sudden deceleration.
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I'd rather have a "line over" than a "nut under".

A line over is a serious malfunction where one or more suspension lines goes over the canopy most always resulting in a cutaway.

A nut under refers to male anatomy and harness straps as it relates to the above mentioned sudden deceleration.
 
lowtimer said:
I'd rather have a "line over" than a "nut under".

A line over is a serious malfunction where one or more suspension lines goes over the canopy most always resulting in a cutaway.

A nut under refers to male anatomy and harness straps as it relates to the above mentioned sudden deceleration.
Click to expand...

:no:

Some of the skydivers that operate here talk about that happening. No thank you! I don't actually know how bad the deceleration is but the sound from the ground is pretty loud and sudden!

N801BH said:
The scale would read less during the decent...
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Under parachute or free falling?
 
The scale will read the same during the descent, assuming the parachute has deployed and speed has stabilized (no acceleration). The formula W=m(g+a) tell us that weight changes are derived from acceleration, not velocity. On the ground you have W=mg because you're not accelerating up or down. On a stable parachute, W=m(g+0), which is the same as W=mg because you're not accelerating there either.

If it helps, think of yourself in a car. Going at 65 vs going at 10, you feel the same. It's only with acceleration or deceleration that you "feel" heavier or lighter.
 
overdrive148 said:
:no:

Some of the skydivers that operate here talk about that happening. No thank you! I don't actually know how bad the deceleration is but the sound from the ground is pretty loud and sudden!



Under parachute or free falling?
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Under parachute...
 
There is no way to answer this question without knowing how fast the conveyor belt is moving.
 
kyleb said:
There is no way to answer this question without knowing how fast the conveyor belt is moving.
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Clearly the load is landing under the parachute so the conveyor belt must be running backwards
 
Norman said:
WHY??
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well....

If a known weight is attached to a scale that is attached to a fixed object then the scale cannot move /give and you get a reliable reading...

If the scale is attached to a parachute, the chute itself is giving up some resistance and the known weight will read less since the parachute is slipping through the air and not rigidly attached to anything.. IMHO..
 
This whole penis should be under a deployed chute. After freefall it's over
 
Geez...
That should have said premis not penis
Autocorrect.
 
N801BH said:
well....

If a known weight is attached to a scale that is attached to a fixed object then the scale cannot move /give and you get a reliable reading...

If the scale is attached to a parachute, the chute itself is giving up some resistance and the known weight will read less since the parachute is slipping through the air and not rigidly attached to anything.. IMHO..
Click to expand...

The bag of coke weghs 100 lbs. Once the 'chute is open and stable the the only forces acting on the scale are the pull down of the bag of coke and the pull up of the parachute. The system is stable or in steady-state.

The pull down of the bag of coke is it's mass multiplied the accelleration of gravity. That product is 100 lbf.

Since the scale is not accellerating the force from the parachue has to equal the pull of the bag of coke or 100 lbf. Any other condition results in accelleration which would change the scale reading.
 
Keep in mind a weight scale is effectively a force gauge.

F=ma

The mass of the object stays the same. During times of acceleration or deceleration the scale will observe a different force (which it displays as 'weight'), but the rest of the time, not.

i.e. The scale will show 100lbs after equilibrium is reached.
 
The gravitational force would be less at altitude so in fact you would see something slightly less than 100 lbs above sea level.
 
There are professionals in Mexico and Central America who have decades of experience with this type of operation. You're asking a bunch of amateurs here.


JKG
 
The correct answer is: who cares, bust out the blow and let's party!
 
Damn Bryan, I bet all of your teachers hated you!
How do you come up with these questions?
 
Does the parachute exert more or equal force compared to the weight of the object?
 
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