Calculating G-Shock of Dropping 5kg Box from 20m

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Discussion Overview

The discussion centers around calculating the G-shock experienced by a 5kg box dropped from a height of 20 meters. Participants explore the theoretical and practical aspects of impact forces, energy dissipation, and the factors influencing deceleration upon impact.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant states that using F=mg leads to an initial assumption of 1G, but questions this based on the height of the drop.
  • Another participant suggests that the material properties of both the box and the surface it lands on are crucial for determining the deceleration and resulting G-shock.
  • There is a proposal to consider the box's density and the density of the ground to estimate the impact dynamics.
  • A later reply introduces the idea that if neither the box nor the ground deforms, it could theoretically lead to infinite deceleration.
  • One participant expresses uncertainty about how to estimate the time frame for energy absorption and the depth of penetration into the ground.
  • Another participant emphasizes the complexity of the problem, noting the numerous variables involved, including material stiffness and orientation during the fall.
  • One participant suggests looking for similar experiments to find realistic values for G-shock measurements.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to calculate G-shock, with multiple competing views on the factors that must be considered and the methods for estimation remaining unresolved.

Contextual Notes

Limitations include the dependence on material properties, assumptions about deformation, and the lack of specific experimental data to inform calculations.

bassplr19
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If I drop a box of the side of a building (20m) that is 5kg, what is the G shock that this will experience?

F=mg is the force, obviously.

Based on basics, I'm coming up with 1G, but that doesn't make sense - the shock is going to be bigger based on the height.

Say I determine the energy that will impact the box, how do I convert that into Gs?
 
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bassplr19 said:
If I drop a box of the side of a building (20m) that is 5kg, what is the G shock that this will experience?

F=mg is the force, obviously.

Based on basics, I'm coming up with 1G, but that doesn't make sense - the shock is going to be bigger based on the height.

Say I determine the energy that will impact the box, how do I convert that into Gs?

You'll need to know what the box is made of and what material it lands on, to know how both will deform. This will translate into how quickly it decelerates to zero.

Your answer should be several orders of magnitude greater than 1. Like 100's or 1000's.

Remember, g's are a measurement of (negative) acceleration. If the box goes from 180mph to 0 mph in a distance of 1cm then you've got quite a few g's.
 
Let's assume that from a 5 story drop it will not deform, the density of the box is 1600kg/m3 and it is impacting dirt at 1900kg/m3.

How do I determine the several orders of magnitude?
 
bassplr19 said:
Let's assume that from a 5 story drop it will not deform, the density of the box is 1600kg/m3 and it is impacting dirt at 1900kg/m3.

How do I determine the several orders of magnitude?

How deep does it sink in the Earth?

If the box does not deform and the ground does not deform then you have an infinite deceleration - infinite g's.
 
I understand that the energy will dissipate over a period of time, but how would I determine (guesstimate) that time frame/energy absorption rate.

I don't know deep it will sink, hence the densities provided.
 
This is more of something that you need to figure out by experimet, or at least some high-end physics software. There's just too many variables to consider, way more than what you have provided. There's the stiffness of the box. The stiffness of the dirt. Their deformations. How the box is oriented when it lands. When if falls (might affect its speed).

The stiffness will change as deformation takes place. Even how you push it off the building would have an effect. I imagine there's even more than that.
 
I guess I assumed this was a homework assignment.

If you're looking for realistic values, I would Google it for similar experiments. Most sensetive equipment has g ratings for undergoing shock.
 

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