Calculating Gforce of Impact from 3ft Fall

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In summary, the conversation is about calculating the gforce of two different impacts - a 220 lb individual falling from 3 ft and a 30 lb object impacting from 3 ft. The speaker is curious about the gforce of the impact that caused bruising and made them unable to walk for a day. The expert explains that it is not possible to know the exact gforce without more information, but gives a rough estimate based on the momentum change and time of impact. The speaker thanks the expert for their help and acknowledges that getting precise measurements for curiosity is not worth risking another injury.
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Cryptic edge
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Ok, so this isn't exactly homework, but it seems the most appropriate spot to post this.

A few days ago I (a 220 lb individual) hit an impact from a fall from 3 ft of my entire weight on a single toe against an unmovable object (tile floor)

I'd like to know the gforce of that impact, assume I came to a full stop nearly immediately

I'd also like to know the gforce of a 30 lb object impacting from 3 ft against a slightly padded object, quick stop though (for comparison with someone who thought I was out of line for getting an X-ray when I couldn't walk after for over a day, who used that as a line of reasoning object impacted a showed foot in this scenario, initial scenario was a bare foot with all force against big toe)

I appreciate any help calculating this that can be given.
 
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We get this question all the time, in different guises. The short answer is that you cannot know without further, detailed information.
You do know the momentum change to be undergone, but that is the integral of force over time. The longer the time the impact is spread over, the lower the peak force can be. An instant stop would imply an infinite force, which clearly never happens.
In the case of your toe, your toe would have come to a stop in much less time than the rest of you. Suppose the whole process took half a second, and the force rose linearly to a peak then fell away linearly at the same rate to 1000N over that time. Your momentum change was 100kg * √(2*9.8) m/s = 443 kg m/s. If I've calculated correctly, that gives a peak of 2358N, or 2.4g.
 
  • #3
Ah. I know when it happened the impact seemed to be an instant stop and the damage to the foot was enough the doc had to double check the X-rays for a break after looking at the bruising. It was a curiosity what the gforce it took to cause that level of bruising since it was enough that made me unable to walk for a day.

I thank you for the help :) I know exact wouldn't have been possible without a lot of precise measurements anyway and that's not something I'm willing to recreate and get those kind of measurements for what amounts to be curiosity. (plus next time I may not be so lucky that it doesn't break lol)
 

FAQ: Calculating Gforce of Impact from 3ft Fall

What is the formula for calculating Gforce of impact from a 3ft fall?

The formula for calculating Gforce of impact from a 3ft fall is G = (2h / t^2) * m, where G is the force of gravity, h is the height of the fall, t is the time of impact, and m is the mass of the object.

How do you measure the time of impact for a 3ft fall?

The time of impact for a 3ft fall can be measured using a stopwatch or a high-speed camera. The stopwatch should be started as soon as the object is released and stopped when it hits the ground. The high-speed camera can capture the entire fall and the time can be calculated from the footage.

Is the mass of the object important in calculating the Gforce of impact from a 3ft fall?

Yes, the mass of the object is an important factor in calculating the Gforce of impact. The higher the mass, the greater the force of impact. This is because the force of gravity is directly proportional to the mass of the object.

What is the maximum Gforce of impact that can be experienced from a 3ft fall?

The maximum Gforce of impact that can be experienced from a 3ft fall is approximately 4.9 G. This is based on the formula G = (2h / t^2) * m and assuming that the time of impact is 0.1 seconds and the mass of the object is 1kg.

Can the Gforce of impact from a 3ft fall be reduced?

Yes, the Gforce of impact from a 3ft fall can be reduced by increasing the time of impact. This can be achieved by using safety equipment such as padding or landing on a softer surface. It is also important to land in a controlled manner to distribute the force of impact across the body.

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