Thunderstruck

Many times in the movies the word "Force" is used (most often in "Star Wars")

But just what is a "force", in physics terms?

It takes a bit of understanding to realise what is happening.

Newton's second Law says that "force = mass x acceleration"....

...but what is "force" ?

A simple example may give an introduction.

It can easily be put into words:

A "force" is " a push which does not stop pushing".

A simple example of which is a car engine.

It "pushes" the wheels against the ground and goes into forward motion. The pushing power is maintained in the gas pedal. Remove your foot, the pushing stops, and the car rolls to a halt because of another "force" - friction. Friction pushes the car the the other way. (if it did not, we would have created "perpetual motion")

So, to keep the car going, it has to push along ALL THE TIME just to keep at the same speed.

In short, a "force" is just "a push which does not stop pushing".

In space, it is different because there are almost no "opposing" pushes, such as friction.

This is why, in space, one "push" is enough.

Point the craft in the direction you want it to go, and use one push (this is called "impulse"). It will go without stopping (Newton's First Law) at a speed that does not change.

If you want it to go faster, keep pushing, and it will. This kind of push is "force", and the longer you maintain this push, the faster the craft will be going when you stop the push.

But supposing you do not stop pushing?

This is the definition of "force". It does NOT stop pushing.

Do we get this in nature? We sure do. Electrostatics is one of the examples. Lightning happens because the electrons cannot stop being pushed to the earth by the "force" of the attraction to it. So the electrons invent their own way of getting there, and the effect is a bolt of lightning (sorry, Doc Brown). The reason that the lightning is never straight is simply because there will always be obstacles, such as as pressure differences, clouds, temperature etc.

This is the best way to view a force. Watch a thunderstorm.

Be thunderstruck!