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## Summary:

- Correct formula to work out impact force of a slamming door?

## Main Question or Discussion Point

Hi Guys,

I am trying to keep this as simple as possible as I only need a ballpark figure. I am sure there are thousands of other variables which need/could be taken into account, but for this purpose, as simple as could be.

A door in my house slams when other doors/windows open.

The door is 72mm(radius for future calculation) wide. I approximate it weighs 16kg(average door weight).

The door is at 90 degrees to it's closing position when it starts to slam.

Using Pi formula, I work out that the diameter would be :

72mm x 2 = 144mm(Diameter)

144 x 3.14 = 452.16mm(Circumference)

452.16 / 4 = 113.04mm(gives me quadrant size)

So distance travelled = 1.13 metre

The time the door took to slam, from start position, was roughly 1 sec.

Therefore I presume velocity= 1.13 m/s

From what I have read...Force/kinetic energy equals "..half the mass x velocity squared... "

So...

Half the mass is... 16kg/2 = 8

Velocity squared of 1.13 = 1.28

So 8 x 1.28 = 10.24

I think the unit is Newtons in this case...

Again, so....in a simplistic formula...would the Impact force of the door closing be 10.24 Newtons?

My second question is probably my main question...

If I put my hand to stop the door(in roughly the same position as where the door frame would stop the door) would the impact force be the same OR is the force dependent on the area(size) of my hand it hits...I'm sure it does.

If I put my finger out(obviously smaller in size) to stop the door I am sure the impact force would be more.

Therefore...what would be the formula to work out impact force on a particular object it hits(hand or finger or anything)..presuming my initial formula is correct at 10.24N ?

I apologize for the simple way I have put this but it's years since I done math and formula.

Please let me know if I have done the formula correct and point out any mistakes(which I am sure there are!).

Thanks in advance.

BTW...I have looked at these related questions but they give indefinite answers or, are far too complex for my understanding...hence why i needed to keep it simple!

https://www.physicsforums.com/threads/how-to-calculate-the-impact-energy-of-a-door-hitting-a-door.821759/

https://www.physicsforums.com/threads/angular-acceleration-velocity-momentum-of-a-door.840398/#post-5273155

I am trying to keep this as simple as possible as I only need a ballpark figure. I am sure there are thousands of other variables which need/could be taken into account, but for this purpose, as simple as could be.

A door in my house slams when other doors/windows open.

The door is 72mm(radius for future calculation) wide. I approximate it weighs 16kg(average door weight).

The door is at 90 degrees to it's closing position when it starts to slam.

Using Pi formula, I work out that the diameter would be :

72mm x 2 = 144mm(Diameter)

144 x 3.14 = 452.16mm(Circumference)

452.16 / 4 = 113.04mm(gives me quadrant size)

So distance travelled = 1.13 metre

The time the door took to slam, from start position, was roughly 1 sec.

Therefore I presume velocity= 1.13 m/s

From what I have read...Force/kinetic energy equals "..half the mass x velocity squared... "

So...

Half the mass is... 16kg/2 = 8

Velocity squared of 1.13 = 1.28

So 8 x 1.28 = 10.24

I think the unit is Newtons in this case...

Again, so....in a simplistic formula...would the Impact force of the door closing be 10.24 Newtons?

My second question is probably my main question...

If I put my hand to stop the door(in roughly the same position as where the door frame would stop the door) would the impact force be the same OR is the force dependent on the area(size) of my hand it hits...I'm sure it does.

If I put my finger out(obviously smaller in size) to stop the door I am sure the impact force would be more.

Therefore...what would be the formula to work out impact force on a particular object it hits(hand or finger or anything)..presuming my initial formula is correct at 10.24N ?

I apologize for the simple way I have put this but it's years since I done math and formula.

Please let me know if I have done the formula correct and point out any mistakes(which I am sure there are!).

Thanks in advance.

BTW...I have looked at these related questions but they give indefinite answers or, are far too complex for my understanding...hence why i needed to keep it simple!

https://www.physicsforums.com/threads/how-to-calculate-the-impact-energy-of-a-door-hitting-a-door.821759/

https://www.physicsforums.com/threads/angular-acceleration-velocity-momentum-of-a-door.840398/#post-5273155