Just a Thought Experiment

[TheAzn]

This is just an idle thought experiment. I think that this has never been discussed before.
We all know that a flying bullet - however light -contain a ginormous amount of force. This is because - though relatively light - bullets travel very fast.

I'm just curious about the equivalent forces generated by heavier but slower moving objects.

Say I have a .50-90 Sharps. Would Arnold S. swinging a giant sledgehammer create an equal amount of force and energy?

 

[Walkalong]

Both would kill you dead.

Sure, they have formulas for figuring energy of various bullets and speeds. Naturally a faster lighter bullet with the same energy as a heavier bullet going slower would act differently on target.

 

[45_auto]

Force and energy are two different things.

If you're impressed by energy numbers, you'll find guns to be very disappointing.

A 460 Weatherby Magnum has about the same amount of energy at the muzzle (7,500 ft lb) as is contained in a typical alkaline AA battery. Peanut butter makes it look even worse, two tablespoons contain about 590,000 ft lb of energy.

Arnold swinging a giant sledgehammer will come no where close to equaling the energy in a AA battery, much less a spoonful of peanut butter.

 

[TheAzn]

A 460 Weatherby Magnum has about the same amount of energy at the muzzle (7,500 ft lb) as is contained in a typical alkaline AA battery. Peanut butter makes it look even worse, two tablespoons contain about 590,000 ft lb of energy.

Arnold swinging a giant sledgehammer will come no where close to equaling the energy in a AA battery, much less a spoonful of peanut butter.

What about force then?

 

[Sam Cade]

What about force then?

http://en.wikipedia.org/wiki/Force

In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate, or a flexible object to deform, or both. Force can also be described by intuitive concepts such as a push or a pull.

Bullets don't have much mass so they aren't very good at imparting motion to things that they impact.

 

[Atom Smasher]

The bullet might not cause a lot of motion in the target due to mass, but the thrust generated by firing a bullet from a weapon can actually be pretty substantial. Check out this (albeit silly) link; if you had the proper weapon, you could launch yourself over mountains

https://what-if.xkcd.com/21/

 

[Cesiumsponge]

Force can simply be calculated as F=ma, or mass times acceleration. A can be substituted with dV/dT but now you're dealing with calculus and related rates.

Energy in kinetic terms is determined by E=1/2mv^2. With that basic formula, you can see an increase in velocity squares the energy gained where's an increase in mass only contributes half. Velocity is king. Not taking into account ballistic coefficients, the less time something spends in flight, the less time gravity has to act upon it.

With colliding bodies, we start getting into elastic and inelastic collisions and kinematic physics, which is still basic algebra. There shound be some java applets and flash demos which allow you to play with the concepts, which give a better feel than just formulas.