# Impact velosity

1. Oct 22, 2008

### bp1945

I am developing a new product. I am currently constructing various prototypes of the product changing only one component using a different material with each model.

I want to test the impact results of each different model dropping a consistent weight (i.e. 20lbs) from a consistent height (i.e. 10’) for each test so video these results to determine which model will best suit my needs.

So, this sounds like a simple question, dropping 20lbs from 20’, what will be the velocity at impact? And is there a simple formula I can use if I change the variables?

2. Oct 22, 2008

### gamesguru

If the products that you are dropping are relatively aerodynamic you can use a very simple formula:
$$v=\sqrt{2ad}$$,
where
v is the velocity when the object hits the ground (ft/s)
a is the acceleration due to gravity (32.17 ft/s2)
d is the height you dropped it from (ft).

3. Oct 23, 2008

### bp1945

I'm not dropping the product, the product will be stationary and paralell to the ground and I will be dropping the weight from a certain height straight down on the product to determine velocity and record (video) impact damage.

And gamesguru, I am worse than terrible at math so that formula scared the hell out of me. Can you do an example using 20lbs as the weight and 10ft. as the distance dropped. What I need to know is the velosity at impact using those two variables. And I may change variables to get different results.

Can you explain this to me in idiot terms?

4. Oct 26, 2008

### gamesguru

As long as you work with fairly heavy weights, the role of air resistance will be negligible and so the weight will not matter, only the height will determine the impact velocity.
If you use my above formula, you will find (in feet):
$$velocity=\sqrt{64.34*height}$$.
You can use google now. To find the impact velocity at 10 feet just type "sqrt(64.34*10)" (without quotes) into google, hit enter. You will get 25.36. This means your weight will hit the product at a speed of 25.36 feet per second.
Hope that helps.

5. Oct 28, 2008

### bp1945

Thanks gamesguru, this helps greatly.