How to Calculate Impact Height for 40 g's Acceleration

[tmifsu530]

Hi everyone,

This may seem like a simple problem but it seems to be escaping me.

Say I have an object of a given mass, m, and I want it to impact the Earth at an acceleration of 40 g's. What height, h, must I drop the object at?

Again, I feel like I'm just missing a step so please let me know how you got there if you can find the answer.

Thanks!

 

[Whovian]

Um? You haven't explained what "impacting at a certain acceleration" means. Do you mean at a speed? g is a unit of acceleration, not velocity.

 

[tmifsu530]

I'm sorry. I want the acceleration that it experiences once it hits the ground to be 40 g's, assuming perfectly inelastic collision with the Earth.

 

[Integral]

It does not matter from which height you drop something, it will never experience greater then 1g acceleration.

 

[tmifsu530]

Nevermind, as I attempted to rephrase the question as I believe I wasn't being clear I worked it out myself! Ha thanks for the help anyway!

 

[Whovian]

I'm sorry. I want the acceleration that it experiences once it hits the ground to be 40 g's, assuming perfectly inelastic collision with the Earth.

Perfectly inelastic? I imagine it would experience infinite acceleration.

 

[hankaaron]

Hi everyone,

Say I have an object of a given mass, m, and I want it to impact the Earth at an acceleration of 40 g's. What height, h, must I drop the object at?

Thanks!

If you are talking about Shock and Vibration measurement, that will depend on the object itself and the properties of the surface that the object falls on.

For instance if you dropped a hard drive from feet feet onto a very plush carpet, you might get 40gs (2ms half-sine). But pull the carpet back and let the drive fall onto bare concrete floor and you'll get over 1,000gs (0.5ms 1/2 sine-wave).