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2.2.2. Energy: Science and Force

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A large part of science, (and particularly in areas where inventing is significant) is about the use of energy in interaction between objects, whether it is atoms within a bending bar or friction between the bar and the table on which it is placed. How many forces do you think can act between two objects? In fact there are only four, as in Fig. 2.5, and even better, two of them are probably not available for you to change, leaving two forces available for simple scientific inventing, electromagnetic and gravity (which we cannot change except by changing the mass of things so the main one we use is electromagnetic).

Fig. 2.5 Four forces

Strong and weak nuclear forces

The strong nuclear force is the strongest force and binds the central parts of an atom together (the protons and neutrons). The weak nuclear force is weaker than the electromagnetic force but stronger than gravity. It affects things inside the atom only and its role is really at the level of quantum physics, (by that we mean complex and small!). Fortunately, for both Strong and Weak forces, their effect is just about zero beyond the distance of the width of an atom so unless you are going to make some pretty big nuclear devices you probably will not be changing these. Except for physicists, these forces can be forgotten about when inventing.

Gravity

Gravity is more than the downward pull of bodies towards the earth, as all bodies attract one another. It is also a very weak force for small or distant bodies, although we do not think about gravity as being weak because we can feel it in our bodies and things we pick up may feel heavy. At a long distance it is the greatest force. For example, there is massive electrical activity in the sun which does not attract metal on earth anywhere near as much as the sun’s gravitational pull.

Gravitational attraction and consequent force is connected with size, which is why the Earth is pulled by the Sun, and distance, which is why the Moon is held in by the Earth and is not pulled away by the Sun. By the time we get down to the size of people and inventions, the force is much smaller.

The bottom line is that although gravity may be a consideration for your inventions, you cannot change it (although as an example of how assumptions can always be challenged, at the time of writing, research is going on into the use of gyroscopes that change their weight when rotating very fast. Perhaps one day we will be able to invent with gravitational forces.)

Where gravitational effects can be played with is in the mass of items. Mass can be changed with different materials, shapes and construction methods such as the judicious use of holes.

Electromagnetic forces

Electromagnetic forces are not just about wires: they are also about how one object holds on to another. Electromagnetic forces are familiar to anyone who has rubbed a balloon on their pullover and stuck it to the ceiling. These are forces that we can play with, and we will discuss them later on.

We are surrounded by electromagnetic fields, which affect how things are attracted or repulsed. These forces also bind atoms and molecules together, and in our world of physical things it is only the electromagnetic forces that count.

When materials are pushed against one another they resist the push through the electromagnetic repulsion in the atoms and molecules. As you push on a material the fields are being pushed together and they resist. Every object resting on another is distorting it by displacing molecules, usually only very slightly. No material is absolutely rigid because it could not be. The force back has to be created by something and that force is electromagnetic. When the force is removed, the material, if it has been elastically distorted only, will spring back to shape.

In chemical bonding, the electrons in the shells of the atoms are shared, which creates a fair to very strong bond, but it is still an electromagnetic force. The glue that sticks your fingers together is the glue of electromagnetism!

When any two objects are placed in contact with one another, the electromagnetic fields of the atoms at the surface of contact will interact with one another, typically resulting in some degree of attraction. A similar attractive effect occurs when molecules are mixed or in solution, such as the way water molecules bonded loosely with salt to make a saline solution.
 

Other parts of this sub-section:

• 2.2.1. Energy: Inventing With Energy
• 2.2.2. Energy: Science and Force
• 2.2.3. Energy: Inventing With Forces

Other sections in this chapter:

• 2.1. What is Science?
• 2.2. Science and Energy
• 2.3. Science and Matter
• 2.4. Science and Space
• 2.5. Science and Time
• 2.6. Simple Science in Non-science
• 2.7. Invention 'So What?'

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