*force*and I could have taken this in a million directions but I had fun yesterday with Archimedes so while yesterday's other word was eureka, today's other word is ouch. Sir Isaac Newton probably said it after an apple dropped on his head causing him to reflect on gravity. Newton figured out how to relate motion and acceleration with force and came up with a series of laws. They pretty much explain how the mechanical universe operates.

Here they are with some practical applications.

**First Law:**An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

An excellent example of this can be seen at about 28 seconds into the clip from

*The Avengers*below.

After winning a battle, The Hulk and Thor are at rest (other than heavy breathing) and aren't going anywhere until The Hulk decides to smash Thor who then goes flying. I think it's fairly safe to say that The Hulk counts as an unbalanced force.

**Second Law:**Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

This brings us to a pretty fundamental equation in the study of physics.

*or F=ma*

**F**orce =**m**ass x**a**ccelerationThis makes sense and seems pretty straightforward. To get Thor airborn, The Hulk would need to smash Thor a little harder if Thor were holding Mjölnir than if he were not. It also takes less force to launch the Falcon into the air than the helicarrier.

**Third Law:**For every action there is an equal and opposite re-action.

No, this is not about a Winchester prank war. This means that for every force there is a reaction force that is equal in size, but opposite in direction. Whenever an object pushes another object it gets pushed back in the opposite direction equally hard. That sounds like the Winchesters anyway. If they are standing back to back and leaning on each other, they are each contributing a force in an opposite direction to maintain their position. If they are holding each other up while standing stationary on the ground, they are in a state of static equilibrium. If they are leaning on each other, holding each other up while they are sitting in the Impala which is moving down the road at a constant velocity, they are in a state of dynamic equilibrium. Maybe that's too much information.

So that is old Newton's take on force. In a wider sense, there are four fundamental forces at work in the universe. Contrary to popular belief, they are not the Armed Forces, force of personality, the sales force or a show of force. They are the strong and weak forces, the electromagnetic force and the gravitational force. The strong and weak forces govern the way atoms are held together. The electromagnetic force which acts between electric charges explains why your hair sticks to a balloon when you rub them together. The gravitational force acts between masses and explains why we stick to the earth. When you have an anvil in the sky and it's speeding downward toward Wile E. Coyote or some plot point, gravity provides the acceleration in the F=ma equation above and now we have F=mg where g is some constant number based on the amount of gravity acting on the falling object. That allows for changes in gravity from Earth to the Moon or Mars.

Why does any of this matter and why should we care? Because by using Newton's laws, we can solve the bane of every student's existence - story problems. Here are some examples. Don't worry, we're not actually going to do math.

If we know Bucky's mass and his rate of deceleration, how far will he slide before he stops?

If Captain America travels at a given speed over a specific distance, will he get to Natasha's in time for lunch?

How much force does Crowley need to exert to keep Sam and Dean pinned to the trees?

If we know the constant of gravity for Middle Earth and the mass of Gandalf and the Balrog, what force will they have when they hit the water at the bottom of their fall?

How much force does Boromir have to use on the doors to keep out the cave troll, (which they do have)?

How much mass must Grond have to smash the gates at Minas Tirith?

If we know the mass and acceleration of the Colt's bullet and how far it traveled to reach Azazel, with how much force did the bullet hit him?

If we know the Impala's acceleration and mass, how much force was delivered to the sign?

If we know the acceleration rate of the falling angels and how far they have fallen, how much mass do they have and how large of a crater will they leave on impact?

If we know the tractor!angel's mass and available force, how much acceleration was created and was it reasonable for a tractor to achieve that?

If the mass of the Samulet is 3g, it falls .5 meters, and the constant of gravity on the earth (not the dark side of the moon) is 9.81 m/s

^{2}, how long will it take to break our hearts and what is it's force on impact?

Ok, so physics is painful. Today's other word is ouch, after all. The Wikipedia article on

*force*also lists a few non-fundamental forces that are notable for fandom.

Friction - at work here between a violin or cello and a bow

Tension - the bridge suspension, not the boys

Elastic forces - anybody with a bungee cord

Fictitious forces - unfortunately, this has to do with physics problems where more than one kind of acceleration or motion occurs, not those of George Lucas.

*Hokey religions and ancient weapons are no match for a good blaster at your side, kid.*

--HAN SOLO, Star Wars Episode IV: A New Hope

Maybe Han was a physicist in his off hours.

May the forces be with you anyway.

caps from home of the nutty and screencapped.net