Of physics, combat and gravity

[MacroQuantum]

I'm trying to get a concept of what low gravity combat would be like. This should come down to a physics problem. A baseball player can throw a baseball at 90 mph. Therefore his hand must be traveling at 90 mph when the ball leaves his hand. So let us assume that in combat the average fist is traveling at just 50 mph, or just 73.3 feet/second (unless someone can reference something more accurate).

Bozer weighs in at 200 pounds, or in 0.2G a mere 40 pounds.

Gozer weighs in at 300 pounds, or in 0.2G a mere 60 pounds.

Bozer throws a punch and connects with Gozer's chin. His fist (roughly a 2 lb object at 1G, or 0.4 lbs at 0.2G) is moving at 73.3 feet/second. Unfortunately, its about here where I get out of my depth. Bozer's fist would have a mass of ? and would impact on Gozer's chin with a force of ?, which would do what to the two objects. Logically, Gozer's chin would would be moved away. But would not the force of the impact also move Bozer away (dependent upon Gozer's mass)?

[Klaynos]

One small note:

 

Pound is a unit of mass NOT weight, weight is a force and measured in Newtons.

 

Mass does not change with different values of gravity.

 

The only significant difference I can see in a low gravity situation (Not! a freefall (commonly, yet incorrectly considered 0g) situation) is that if you hit someone upwards away from the major gravitational body then they would move further upwards than in a higher gravity situation.

[swansont]

One small note:

 

Pound is a unit of mass NOT weight' date=' weight is a force and measured in Newtons.

 

 

[/quote']

 

 

Pounds are indeed a unit of weight; Newtons are the SI version. The mass unit in the English system is the slug. Engineers sometimes use the unit pound-mass (lbm) which is a mass equivalent at 1 g of acceleration, but they are to be scorned for this.

[MacroQuantum]

Wouldn't the same hold true on the horizontal as well? I don't know how hard Bozer hit Gozer (in pounds?) but wouldn't it potentially move him (or both) along the horizontal plane a significant distance?

[ecoli]

Wouldn't the same hold true on the horizontal as well? I don't know how hard Bozer hit Gozer (in pounds?) but wouldn't it potentially move him (or both) along the horizontal plane a significant distance?

 

Yes, and in opposite directions.

[Klaynos]

My appologies, I was sure that a pound is a fraction of a stone, I was unaware of it's use for force...

 

It would make a horezontal difference only if the reduction in weight (and therefor reduction in the "Normal" force from what they are stood on) lead to a significant and noticiable effect on the friction they are experianceing from the ground.

[ecoli]

It would make a horezontal difference only if the reduction in weight (and therefor reduction in the "Normal" force from what they are stood on) lead to a significant and noticiable effect on the friction they are experianceing from the ground.

 

For some strange reason, when I saw the title of the post, I assumed your were talking about a lack of gravity... that's weird, why would I think that? Anyway, so you can ignore my last post.

[MacroQuantum]

That being my general point Klaynos. I'm trying to get a grasp on how hard someone would have to hit something to move that 80 pounds, assuming it's not braced against a wall, etc. Friction from the ground, I would tend to say would be negible since the only surface of that 80 pounds on the ground (to experience resistance) would be about 2 feet.

I supose the real question would be: what kind of force would the fist connect with.

[Xyph]

Perhaps I'm wrong, but it seems to me that if you disregard friction and neither the hitter nor the hittee has anything to brace themselves on, it wouldn't matter how you hit anything - both the involved would just bounce of each other in opposite directions. Gozer would probably be moving more slowly, though, since he has greater mass.

[Klaynos]

Perhaps I'm wrong, but it seems to me that if you disregard friction and neither the hitter nor the hittee has anything to brace themselves on, it wouldn't matter how you hit anything - both the involved would just bounce of each other in opposite directions. Gozer would probably be moving more slowly, though, since he has greater mass.

 

 

Yes if you disregard friction they would move away from each other each with exactly the same magnitude of momentum. But this leads to the question how could they walk if there was no friction, and also wouldn't punching change your momentum/angular momentu enough against the air pressure and the fact angular momentu has to be constant and your changing your centre of gravity etc with your arm moving to throw you off ballance... :|

[MacroQuantum]

Let's see if I can't simplify the problem. A 0.4 pound object moving at 73.3 feet per second would impact on an object at ? (pounds per square inch?). If object is 2" x 4", this then would give it a total surface of 8". If amount of impact (?) is greater than 60 pounds then target should get knocked on his asterisk (?). Or am I missing something?

[Jacques]

Gravity is not involve in that problem. Something with mass x and speed v hitting something else with mass y and speed 0 will always give the same impact no matter if it is on the moon or on earth or in space.

You must know the difference between mass and weight to understand that.