How to Calculate force exerted on a falling body?

[Chandrasekar]

TL;DR Summary

want to calculate force exerted on a body for that i need to calculate time duration on impact.

I'm curious about impact on falling object, so i have taken initiative to solve this problem.
I considered only force on the falling object would be its weight and taken F=mg. With only limited data m=.25kg and drop height h=1m.
Pondering on this consideration practically, it will have more force than its actual weight.
After Studying on various resources:
1. Link1
2. Link2
3. Link3
4. Link4
5. Link5
6. Link6*
7. Link7*
From this studies i have taken that i need to consider Momentum of the falling body and weight of the body. But in all the solution IMPACT TIME is assumed.
how do i calculate this impact time?

 

[Baluncore]

Welcome to PF.

You assume a drop height of 1 metre.
What does it then impact ?
How much time does it take to stop ?

 

[Chandrasekar]

concrete - rigid base.
How much time does it take to stop ? This is what i want
I can calculate falling time.
i can't calculate the impact time and time taken to stop the object from initial velocity of the impact and 0 final velocity.

 

[Ibix]

How much time does it take to stop ?

It depends on what your object is made of and what the floor is made of, and their shapes. This is because the answer depends on how easy it is to deform the object. If you idealise both object and floor as perfectly rigid then the answer is zero time. If, on the other hand, you think of a water droplet then it's just going to splash, and the answer will be on the order of the time it takes the top of the droplet to hit the floor after the bottom touched (over-simplification warning!).

It's a difficult question - there is no single simple formula.

 

[PeroK]

i can't calculate the impact time and time taken to stop the object from initial velocity of the impact and 0 final velocity.

This is what you need to do: either by your own experiments or researching the topic online. The impact time will also depend on the object. E.g. the force (per unit mass) of impact for a soft object will be less than for a hard object.

 

[Chandrasekar]

i can understand that it depends upon objects elasticity (material property), structure of the body and some energy will loss as heat, then how to calculate it?. what formula do i have to use in order to find it.

The final result, when i drop an object from a height i want to know what will happen to the object, will it break, or damage, solid.

for example when i drop a bottle i want to calculate how much damage it get.

At the beginning it seems very simple problem, as time stretches on study it become complicated to solve :(

 

[PeroK]

i can understand that it depends upon objects elasticity (material property) and structure of the body, then how to calculate it?. what formula do i have to use in order to find it.

You need data on the properties of the materials involved.

The final result, when i drop an object from a height i want to know what will happen to the object, will it break, or damage, solid.

You need experimental data. There isn't just a single formula. Think about the car crash testing that gets done.

 

[Baluncore]

Use a thick carpet, or a crumple zone, to lengthen the time it takes to stop.
https://en.wikipedia.org/wiki/Crumple_zone

 

[Chandrasekar]

Thank you for all who responded to my request, i didn't expected this much response for my query.
but still, even its complicated i want to how to solve it.

 

[Lnewqban]

Thank you for all who responded to my request, i didn't expected this much response for my query.
but still, even its complicated i want to how to solve it.

Using an accelerometer would be the most precise test to perform.

You can at least estimate a reasonable maximum distance the floor and body will deform during impact.

Copied from
https://en.wikipedia.org/wiki/G-force

”After a free fall from a height

followed by deceleration over a distance

during an impact, the shock on an object is

· ɡ0. For example, a stiff and compact object dropped from 1 m that impacts over a distance of 1 mm is subjected to a 1000 ɡ0 deceleration.”

 

[jrmichler]

At the beginning it seems very simple problem, as time stretches on study it become complicated to solve

True statement. Even for people who do this every day.

There is some good discussion of this in this thread: https://www.physicsforums.com/threads/greater-momentum-on-impact-means-greater-force.1049141/. While that thread is about cars smashing into walls, the principles are the same: a rigid impact has higher forces than a soft impact. And it is not always possible to calculate the hardness of the impact, and the resulting forces.

 

[Chandrasekar]

True statement. Even for people who do this every day.

There is some good discussion of this in this thread: https://www.physicsforums.com/threads/greater-momentum-on-impact-means-greater-force.1049141/. While that thread is about cars smashing into walls, the principles are the same: a rigid impact has higher forces than a soft impact. And it is not always possible to calculate the hardness of the impact, and the resulting forces.

i can't find definite answer from this thread. (sorry but on my perspective people are complicating a simple question)

 

[Ibix]

i can't find definite answer from this thread.

There wasn't an answer in that thread. There were about 700 different attempts to get the first poster to realise that he had a contradictory mental model of how a crash happened, but no resolution.

sorry but on my perspective people are complicating a simple question

As they say, "to every question there is an answer that is both simple and wrong". This is one where there is no simple right answer.

This is basically why crash test dummies exist - there isn't a way of working out forces during a car crash except to build a car and slam it into a wall and see what happens. You might be able to build a computer model these days, but I would suspect anything that isn't a cuboid of perfectly elastic material landing flat on one face isn't tractable analytically.