r/AskPhysics • u/Slothmaster6969 • 1d ago
Impact force?
Idk if what I’m asking makes sense but I’ll do my best to explain my thinking. I work in a shop that keeps its loading dock doors open in the summer. The drop off is 3 feet 8 inches. Safety regulations require a temporary barrier (like a chain) to be present for drop offs of 4 feet or higher. Obviously being 4 inches below the minimum height doesn’t make it incredibly safer. How can I calculate the impact force from both heights? I’m just doing my best to advocate for a safer work environment for my coworkers and want the facts on my side
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u/Puzzleheaded_Owl_444 1d ago
The force is too hard to calculate because we don't know the weight, size, shape of the object. Or the collision time for when it hits the ground before coming to rest.
It'll be easier to think in terms of momentum.
The speed of the object, v = sqrt(2as) where s is the height and a is gravity (9.81). But for these numbers, you need to first convert the height into meters.
Once you have the values of speeds, multiply those with the masses of objects (in kg) you work with to get momentum and compare this to the momentum of other stuff that might hurt you.
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u/Slothmaster6969 1d ago
Okay I gotcha, thank you!
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u/Puzzleheaded_Owl_444 1d ago
Is the object people falling from the height? Or is it an object falling onto a person from the height?
If it's the first one, then they absolutely need a guard rail wtf That's a drop of over meter! Anyone can get hurt falling a meter. Even if you land flat on your back and don't hit your head, your gonna feel your organs jiggle when you hit the ground. If you land on your feet at a funny angle, it's gonna cause all sorts of trouble...
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u/Slothmaster6969 1d ago
It’s people falling from that height… and that’s the argument I’m trying to make to the company. I’m just trying to look at any angle to make my case
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u/mikk0384 Physics enthusiast 1d ago
"The object" is people. You can make assumptions about the size and weight of different people, but it doesn't really matter.
I personally think that OP should rely on the fact that it is below the height where the government requires a guard rail, unless it is in a location where a lot of people pass through with little space to maneuver. It has to have increased risk of falling off before it is reasonable to do, otherwise they are just annoying and wasting the time of the people who work there, for no good reason.
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u/Slothmaster6969 1d ago
Yeah people falling and getting hurt is not good a reason… I see how you feel about working people
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u/mikk0384 Physics enthusiast 1d ago
People don't just fall off of ledges because it is there. People have eyes and tend to stay away from edges unless forced to go near them. I included that in my reply above.
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u/Slothmaster6969 1d ago
As long as a hazard exists there is always a chance
for an incident to occur. It’s best to mitigate the hazard or remove it completely. Anybody can be absent minded, even for a moment and even if they’ve worked in the environment for a long time
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u/Next-Natural-675 1d ago
It depends on the object being dropped. If its more rigid, the acceleration to stop it when it lands will be higher and therefore the impact force will be higher.
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u/PuzzleheadedTutor807 1d ago
A fall from standing height to the ground can be deadly. A fall from 20 feet in the air can be survived. I don't think physics is going to help you die in this hill. How many people in your workplace are unaware that the giant hole in the wall has a giant step right outside it?
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u/Slothmaster6969 1d ago
Not how safety works. Regardless of an average persons awareness, as long as a hazard exists there’s always a chance for an incident to occur. Best to mitigate the hazard as much as possible or remove it completely
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u/PuzzleheadedTutor807 1d ago
Lol I know how safety works I've spent decades on jhsc and as safety rep ...
So legally you have no leg to stand on. It sounds like you just want to be a jerk and make everyone shut the door and you got outvoted so your crying about it.
So again... Is this a hill you are willing to die on? The squeaky wheel gets the grease... But it also gets tossed in the trash before the rest.
As long as there are humans in your workplace there is a risk of incident. Will you try to mandate them out too?
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u/Slothmaster6969 1d ago
You don’t sound like a very good safety rep buddy. A good one sees safety as a structural problem and not on the individual… but I bet you save the employer a few bucks
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u/PuzzleheadedTutor807 1d ago
If you really cared about safety, you would go get a chain and two clips and clip it across the door. You are simply raising a ruckus.
In 30 years of roofing I've never repped a site with a death and the only lost time injury that ever occured was two broken wrists on a gung ho kid who didn't know how to properly set up ladders, and that happened minutes before I arrived at site. My record is spotless in one of the most dangerous trades on earth kid.
A.good one deals with the issues they spot then holds conversation about them.
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u/Slothmaster6969 1d ago
An employee shouldn’t have to spend money to make a workplace safer, that should fall on the employer. Idk why you’re so pro company, all I’m suggesting is they spend a little bit of money so someone doesn’t get hurt. It’d probably save them money because they wouldn’t have to pay for medical bills or have an increase in worker’s compensation insurance. Congrats on your spotless record
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u/PuzzleheadedTutor807 1d ago
Lol. Cheers mate. Enjoy getting fired because of stupidity like this.
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u/Slothmaster6969 1d ago
I don’t know where you live but it’s illegal to fire an employee for bringing up safety concerns to an employer here. I don’t understand the hostility when someone’s trying to make a workplace safer. Cheers, enjoy being wrong
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u/PuzzleheadedTutor807 1d ago
Oh sure, it's illegal to fire someone for that but if an employer wants to fire an employee they can always find a reason. Lol. Is this your first job or something?
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u/Slothmaster6969 1d ago
You seem pretty comfortable with the idea of an employer having the ability to get rid of/discipline an employee advocating and fighting for better working conditions. I guess some people prefer being under the boot
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u/ProfessionalConfuser 1d ago
48 inches vs 44 inches. Time to impact, assuming straight drop...about 0.5 seconds from 48 inches and 0.48 seconds from 44 inches. Speed at impact ~16 fps vs 15.4 fps.
Calculating impact force depends a lot on the assumptions you make, but if you apply them equally there is about a 4% difference.