Can anybody give me a really good yet simple definition/explanation of force. I know it is a push, pull, or twist on an object, but what is it exactly. The rate of energy input? i know the units are neutons or (Kg*m)/s^2 but what does that mean. Is force related to energy or work or potential energy? Could somebody please explain

force can do a lot of things
if you have force times a mass, you can find the rate at which that mass accelerates due to that force
F=MA

if you have force over a distance then you can find the work done on that object by pushing it over a distance with a constant force
f*d=w

or if you arent moving anything, force can be used also, pressure is a function of force.
pressure is force over a certain area,
like pounds per square inch or PSI like in car tires.

in the first two, motion is invloved,
but in the third example, motion is not involved.
I tend to think of force as the transfer of energy.
you exert energy to put a force on something to put it in motion, or put a force into storage of energy, like in compressed gas like the tires.


hope this helps, i tried to explain it the best way i could without getting too technical,
feel free to ask me any questions.
-chris

"The amount of pressure exerted on a body is FORCE."

(as explained by the equation F=ma)
Newton=kg*metre/sec^2

This force can be in any direction; which can pull,push, bend ,twist,accelerate etcetra.
The equation you gave(kg/m^2) is the defintion of pressure, not Force, which is measured in Pascals.
Anyhow, coming back to the rest of your Querie.
Force can be related to Energy as
Potential Energy = mgh (where m is mass, g is gravitational pull and h is height.)
and F= mg so
PE = F*h

When an object falls, as a potential difference is created, electrical energy is produced. Thus, one can say F is related to PE.

WorkDone = Energy = Force*Distance

Although my answer isn't as comprehensive as Bibc14 and doesn't encompass as many aspects_ I hope it satisfies you.

Enjoy your Mechanics!

Physics) Any action between two bodies which changes, or tends to change, their relative condition as to rest or motion; or, more generally, which changes, or tends to change, any physical relation between them, whether mechanical, thermal, chemical, electrical, magnetic, or of any other kind; as, the force of gravity; cohesive force; centrifugal force.

now are you Happy?

PiN~Jinx

I won't pretend to offer anything more than what has already been said, but you wanted a simple explanation and simple is exactly how I think, so it should work out.

The easiest way to remember when a force is or is not acting on an object is by using the laws of motion (object will stay still unless acted on by a force; object will move at steady speed in a straight line...etc.)

Force is not the rate of energy input! This is what I thought for some time before starting AS physics, but it becomes apparent when you derive the formula for kinetic energy that it is not the case.

E[sub]k[/sub] = ½mv²

E[sub]k[/sub] = kinetic energy, in joules
m = mass of object, in kilograms
v = speed of object, in metres per second

A force of 1 newton (symbol for newtons is N, so 1N) applied to a shoe of mass 1kg will cause it to accelerate at 1m/s². This is fairly obvious, and you can easily see how a force of 2N with 1kg will double the acceleration while a force of 1N with 2kg will halve the acceleration. The link between these three things is therefore:

F = ma

F = force, in newtons
m = mass, in kilograms
a = acceleration, in metres per (second²).

Thinking back to the 1N acting on the 1kg shoe, the shoe will gain speed at a rate of 1m/s/s (1 metre per second, per second - this is the same as writing 1m/s²). It gains speed at a steady rate, but it gains energy at an increasing rate because of the formula E[sub]k[/sub] = ½mv². To show this, imagine the difference in the speed of the shoe between (these are random figures) 3m/s and 4m/s, and the difference in speed between 40m/s and 41m/s...both 1m/s. But the energy difference between 3 and 4 is 3.5J, and between 40 and 41 it is a much higher 40.5J.

I will leave it to you to understand why that is, as I have no idea.

Getting back to the question, force is related to work as people have stated above:

W = Fd

W = work, in joules
F = force, in newtons
d = distance moved in an exactly opposite direction to the force F, in metres

For this one I picture my friend, the shoe, sitting on an area of flat ground somewhere on the Earth. The force acting downwards on the shoe (mass 1kg) is equal to about 9.81N. This is due to the Earth's gravity pulling down with a force of 9.81 newtons per kilogram. If I raise the shoe up, I am forcing it to move in the exact opposite direction to the gravitational force of 9.81N. This causes the shoe to gain potential energy (that is to say, it is now able to fall down and get kinetic energy). Another way of putting this is to say that the shoe "does work". You can see how, if I raise the shoe by one metre it gains 9.81J of kinetic energy, and if I raise it by two metres it gains 19.62J...etc. It doesn't matter how quickly or slowly I raise the shoe, it will always gain a certain (F x d) amount of energy, and the energy is directly proportional to the distance it is raised. I realise I have probably just answered what you already knew…

P.S. I think you got your unit of force (kg*m/s²) perfectly correct.