Calculating Punches that throw people across the room

Majin Gojira · Post by **Majin Gojira** » 2003-01-19 02:35am

It's been a tick in my head for a little bit. It happens on many programs. Superpowered character A fights random human B and sends them flying across the room.

I'm trying to figure out how to calculate the Force needed to do this, but I'm no physist. Any takers on trying to figure this out?

Enlightenment · Post by **Enlightenment** » 2003-01-19 02:58am

It's not always possible to calculate the forces involved in these kind of incidents because the kinematics of the victim don't follow physical laws. To approximate the cases that can be calculated:

In order to throw someone X meters horizontally, they must be lifted above the ground by a height (Y), be accelerated (a) to a velocity (v) high enough that they will hit the opposing wall before the force of gravity drops them from Y to ground level.

In Earth gravity (9.8m/s^2) and using SI (metric) units:

The fall time for an object lifted to y meters is defined by

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t = sqrt (2y/9.8)

In order to throw a person x meters in time t the velocity v must be

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v = x/t

In order to impart velocity v to the victim within the distance x that the punch contacts the victim's body, the acceleration a must be:

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a = sqrt(v^2/2x)

Finally, the force required to accelerate an object with mass m to acceleration a is defined by

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F=ma

The result will be in Newtons.

Note that this is only an approximation. It does not consider air resistance, friction with the floor (e.g. if the victim's feet drag), slope of the floor, or situations where the victim is thrown upwards.

AWACS · Post by **AWACS** » 2003-01-19 06:20am

Lets say the person is thrown a distance of 40 feet and describes a proper physics-obeying parabolic arc as they go through the air. When they hit the wall, they're about three feet from the ground.

Then use that as a basis.

Majin Gojira · Post by **Majin Gojira** » 2003-01-19 10:57am

Usually when this event is displayed, they are thrown upwards as well...sorry to complicate things.

Post by **AdmiralKanos** » 2003-01-19 10:59am

The fact that the person is not killed immediately or fatally injured by the punch indicates that it is a non-physics situation: the force required for the correct ballistic arc would kill a man.

Majin Gojira · Post by **Majin Gojira** » 2003-01-19 02:36pm

Cave in their rib cage, crush organs, would the impact be great enough to snap their neck or is it all of the above and then some?

Admiral Griffith · Post by **Admiral Griffith** » 2003-01-19 05:53pm

I'd say the latter of the two.

I dunno, though.

Shaka[Zulu] · Post by **Shaka[Zulu]** » 2003-01-19 11:16pm

well, it does depend on the magnitude of the force applied and the actual kinematics of both the application of the force and how the victim is releived of that energy (how he impacts). The human body is surprisingly resilient -- with the exception of the head itself -- and that resilience can be enhanced somewhat thru the use of certain techniques (breakfall). As an example, I was riding my old 12-speed bike down a road one night (doing about 35mph... I was pretty fast at the time), when the chain jumped the gears & locked the rear wheel... luckily I felt it as it did so, and performed what can only be described as a textbook example of a controlled ejection -- leveled my feet on the pedals & the moment the bike started to to come out from under me, jumped. Hit the pavement palms first ( preventing a chin strike), then chest, & skidded for about 20ft after 'flying' superman style for about 30. Skinned my hands, elbows & knees a bit (no scars)... ruined my shirt and made some holes in my pants, but otherwise none the worse for wear. Needless to say it could have bee MUCH worse & I havent ridden that bike since!

Post by **Darth Wong** » 2003-01-19 11:19pm

Shaka[Zulu] wrote:well, it does depend on the magnitude of the force applied and the actual kinematics of both the application of the force and how the victim is releived of that energy (how he impacts). The human body is surprisingly resilient -- with the exception of the head itself -- and that resilience can be enhanced somewhat thru the use of certain techniques (breakfall). As an example, I was riding my old 12-speed bike down a road one night (doing about 35mph... I was pretty fast at the time), when the chain jumped the gears & locked the rear wheel... luckily I felt it as it did so, and performed what can only be described as a textbook example of a controlled ejection -- leveled my feet on the pedals & the moment the bike started to to come out from under me, jumped. Hit the pavement palms first ( preventing a chin strike), then chest, & skidded for about 20ft after 'flying' superman style for about 30. Skinned my hands, elbows & knees a bit (no scars)... ruined my shirt and made some holes in my pants, but otherwise none the worse for wear. Needless to say it could have bee MUCH worse & I havent ridden that bike since!

The fact that you skidded for 20 feet is the reason you were not killed. If you had slammed face-first into a brick wall at 35 mph, you would be dead now. When someone punches someone in the chin and sends him flying halfway across a room, the moment of fist-to-face impact is much more analogous to flying into a wall face-first.

Shaka[Zulu] · Post by **Shaka[Zulu]** » 2003-01-20 12:22am

Darth Wong wrote:The fact that you skidded for 20 feet is the reason you were not killed. If you had slammed face-first into a brick wall at 35 mph, you would be dead now. When someone punches someone in the chin and sends him flying halfway across a room, the moment of fist-to-face impact is much more analogous to flying into a wall face-first.

ummm... didnt I say that?