How Does Positive Lift Affect the Ascent Rate of a Heavily Loaded Truck?

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Discussion Overview

The discussion revolves around the effects of positive lift on the ascent rate of a heavily loaded truck when connected to a helium balloon. Participants explore the concepts of buoyancy, lift, and the relationship between mass and ascent rate, with a focus on theoretical scenarios rather than practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant proposes that removing a one-pound rock from a neutrally buoyant truck results in a positive lift of one pound, suggesting it would rise similarly to a small balloon with the same positive lift.
  • Another participant agrees that the truck has a positive lift of one pound but argues that due to its large mass, the ascent would be minimal compared to a small balloon.
  • A further claim questions whether the ascent rate of a heavily loaded truck with one pound of positive lift would be inversely proportional to its mass, suggesting a potential calculation method for ascent rates of massive bodies.
  • There is a clarification regarding the terminology, with participants confirming the use of "pound-force" in the context of lift.

Areas of Agreement / Disagreement

Participants generally agree that the truck experiences positive lift when a weight is removed, but there is disagreement on the implications of this lift regarding ascent rate and the relationship between mass and lift. The discussion remains unresolved regarding the exact nature of the ascent rate calculations for large masses.

Contextual Notes

Participants express uncertainty about the relationship between lift and ascent rate, particularly in the context of different masses. There are also unresolved questions about the calculations involved in determining ascent rates for large objects.

Who May Find This Useful

This discussion may be of interest to those exploring concepts of buoyancy and lift in physics, as well as inventors or engineers considering applications involving large masses and buoyant systems.

Syed F. Karim
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Let's say that I rig up a truck to a giant helium balloon, but I load up the back of the truck with enough stones so that the truck has reached a state of neutral buoyancy--its just floating in mid-air, not rising not falling, just there. Now let's say I take away a one-pound rock from the truck's bed. Does the truck now have a positive lift of one pound? And will it now rise just like a small balloon with one pound of positive lift?
 
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Originally posted by Syed F. Karim
Let's say that I rig up a truck to a giant helium balloon, but I load up the back of the truck with enough stones so that the truck has reached a state of neutral buoyancy--its just floating in mid-air, not rising not falling, just there. Now let's say I take away a one-pound rock from the truck's bed. Does the truck now have a positive lift of one pound? And will it now rise just like a small balloon with one pound of positive lift?

Yes, when the truck has neutral buoyency the forces acting on it perpendicalr to the ground are in equilibrium, by removing 1 pound you are removing 1 pound* from the downward force which means that there will be a net lift of 1 pound*.

* Isn't it pound-force? I I've never used anything other than the SI system in mechanics.
 
Yup. Pound-force.

- Warren
 
Originally posted by Syed F. Karim
Let's say that I rig up a truck to a giant helium balloon, but I load up the back of the truck with enough stones so that the truck has reached a state of neutral buoyancy--its just floating in mid-air, not rising not falling, just there. Now let's say I take away a one-pound rock from the truck's bed. Does the truck now have a positive lift of one pound? And will it now rise just like a small balloon with one pound of positive lift?

Yes it has positive lift of one pound, but No it does not rise just like a small balloon. It still has very large mass, so that one pound lift results in very small acceleration.
 
Yes it has positive lift of one pound, but No it does not rise just like a small balloon. It still has very large mass, so that one pound lift results in very small acceleration.

If a small balloon with a positive lift of one pound has an ascent rate of 1000ft/min, would a 1000lb-truck with the same one-pound positive lift have an ascent rate of just 1ft/min? Is it an inverse relationship? How do you calculate the rate of ascent of massive bodies? (This is not a homework problem, I am an inventor.)
 
Originally posted by Syed F. Karim
If a small balloon with a positive lift of one pound has an ascent rate of 1000ft/min, would a 1000lb-truck with the same one-pound positive lift have an ascent rate of just 1ft/min? Is it an inverse relationship? How do you calculate the rate of ascent of massive bodies? (This is not a homework problem, I am an inventor.)
a=f/m
 

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