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

[bassplr19]

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?

 

[DaveC426913]

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.

 

[bassplr19]

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?

 

[DaveC426913]

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.

 

[bassplr19]

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.

 

[Lsos]

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.

 

[DaveC426913]

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.