Introduction to forces and pressure

A force is a push, pull or a twist

Pressure is continuous physical force exerted on or against an object by something in contact with it.

F = P pa

A

E.G. 100 = 50pa

2

The more surface area something has the less pressure it exerts, because the force can be spread out more.

If a Tank ran over your foot, it probably wouldn't break your foot (but it will do some damage, so don't go get your foot ran over by a tank!)

Although a ballerina could impale your foot if he/she stood on your foot with her tiptoes!

There are may different forces, but we'll just cover a few of the crucial ones.
Contact:

• Upthrust
• Friction
• Air resistance
• Water resistance
• Drag

Non – contact:

• Gravity
• Electro magnetism
• Magnetism

Quantum Phisics

Quantum mechanics (QM; also known as quantum physics or quantum theory), including quantum field theory, is a fundamental branch of physics concerned with processes involving, for example, atoms and photons. In such processes, said to be quantized, the action has been observed to be only in integer multiples of the Planck constant. This is utterly inexplicable in classical physics. Quantum mechanics gradually arose from Max Planck's solution in 1900 to the black-body radiation problem (reported 1859) and Albert Einstein's 1905 paper which offered a quantum-based theory to explain the photoelectric effect (reported 1887). Early quantum theory was profoundly reconceived in the mid-1920s. The reconceived theory is formulated in various specially developed mathematical formalisms. In one of them, a mathematical function, the wave function, provides information about the probability amplitude of position, momentum, and other physical properties of a particle. Important applications of quantum mechanical theory[1] include superconducting magnets, light-emitting diodes and the laser, the transistor and semiconductors such as the microprocessor, medical and research imaging such as magnetic resonance imaging and electron microscopy, and explanations for many biological and physical phenomena. There is a picture of some hydrogen atoms above this text, you might be thinking "where are the electrons?" Well the wave functions around the nucleus  are the electrons, those wave functions are places the one or two electrons could be, this only happens on the electrons, not the whole atom itself because the electrons are quantum / sub-atomic.

Air resistance

Air resistance is air pushing against a moving object. The air pushes on the object as the air gets out of the way to let the object through. If you've ever been on a rollercoaster, or cycled fast down hill, you might have felt this air resistance as a wind on your face.

Friction

Friction is a force between two surfaces that are sliding, or trying to slide, across each other. Friction always slows a moving object down. Air resistance is a type of friction.

Here is the formula describing friction

 If this is too complicated, here is a picture.

To pull it all together, here is a video

Upthrust

If you try to lift up a weight in a swimming pool and then try to lift the same weight on the edge of the pool, it feels much lighter in the water.

This was supposed to have been first explained by the Greek scientist Archimedes. He said that the water gives an upward force or upthrust on any object in it.

You can weigh an object in air and then in water and actually work out the upthrust, it is the difference between the two readings. For this reason the upthrust is often called the loss in weight of the object.

Here is a video that I think explains this principle well;