# Energy, Forces and Fields

## Scientific Laws

• Nominative statements that describe some aspects of the universe

• Do not necessary offer an explanation of how the universe operates

• Derived from observations (they just describe it)

• Often have a mathematical form

• Can be used to predict/ calculate further observations

• Like hypotheses and theories, they cannot be proved (for example, newtons laws of motion can be used to make predictions about the motion of objects)

• Laws may have exceptions and may be accepted/ modified in light of new evidence

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## Newtons First Law of Motion

‘Every object in a state of uniform motions tends to remain in that state of motion unless an external force is applied to it’

It doesn’t matter what kind of force is exerted on the object, all will affect its motion.

Force= something that exerts a push or a pull on an object or changes its shape.

Forces are measured in Newtons (N)

Forces are vectors. This means that not only do they have a numerical measurement but they have a direction too.

If an object moves in a circle, the constantly changing force points to the centre of the circle. This force is called a centripetal force.

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## Newtons 2nd Law of Motion

The relationship between an objects mass m, its acceleration a, and the applied force F is F=ma.

Mass is a measurement of how much stuff is in an object. i.e. how many particles/atoms are in something

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## Newtons 3rd Law of Motion

Newtons 3rd Law of Motion= Every action has an equal but opposite reaction

A field is said to exist when an object can exert a force on another object at a distance.

For example: A gravity field

A electrostatic field

A magnetic field

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## Gravity

Comparative to other types of forces, gravity is a weak force between objects. It depends on two factors:

• Mass of objects

• Distance between the objects

Gravity is a relatively weak force. It is the force attracting two objects together. It is only noticeable with very large objects.

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## Electromagnetic Unifying Theory

Electromagnetic Unifying Theory

• All matter is made out of atoms

• Atoms are made out of positively charged nuclei and negatively charged electrons. Therefore, atoms have an electric field

• When electrons move through an electric field, the electromagnetic radiation is emitted

• The higher the frequency of the movement, the higher the frequency of the EMR in the form of a transverse wave

• This EMR wave carried both an electric force and an magnetic force

• The wave travels at the speed of light

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## Systematic and Random errors

• Errors involved within the system of the experiment

• These errors never go away

• Can only be checked by performing the experiment with different apparatus

• When systematic errors are small, the data is said to be accurate.

Random errors

• These are inconsistent errors that can vary every time the experiment is done

• Better experimental design can help reduce random errors

• Best way to deal with these is to repeat the experiment sveral times and calculate the average results

• The range of the data gives an indication of the size of the random error (e.g. error bars on a graph)

• Readings with small random errors are said to be precise

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