The "objects" are just the things the force acts between. Different forces act between different sorts of object. For example, gravity acts between objects with mass, like the sun and the earth. Another example is electromagnetic force, which acts between objects with charge, like an electron and the nucleus of an atom. "Gravity" and "electromagnetic force" are two examples of forces.
A force changes the state of an object (some physical quantity changes) or, strictly, the states of two objects, since the force is an interaction. For example, a force causes an affected object to be pushed or pulled in a certain direction. This changes the object's momentum. Forces cause objects to accelerate, add to the object's overall pressure, change direction, or change shape. The strength of a force is measured in Newtons (N). There are four fundamental forces in physics.
A force is always a push, pull, or a twist, and it affects objects by pushing them up, pulling them down, pushing them to a side, or by changing their motion or shape in some other way.
According to Newton's Second Law of Motion, the formula for finding force is:
where formula_2 is the force,
formula_3 is the mass of an object,
and formula_4 is the acceleration of the object.
This formula says that when there is a force on an object then it will move faster and faster.
If the force is weak and the object is heavy, then it will take a long time to increase the speed very much,
but if the force is strong and the object is light, then it will move a lot faster very quickly.
Gravity is an acceleration. Everything that has a mass is being pulled toward the Earth because of that acceleration. This pull is a force called weight.
One can take the equation above and change formula_4 to the standard gravity "g", then a formula about the gravity on earth can be found:
where formula_7 is the weight of an object,
formula_3 is the mass of an object,
and formula_9 is the acceleration due to gravity at sea level. It is about formula_10.
This formula says that when you know the mass of an object, then you can calculate how much force there is on the object because of gravity.
You must be on earth to use this formula. If you are on the moon or another planet, then you can use the formula but "g" will be different.
Force is a vector, so it can be stronger or weaker and it can also point in different directions.
Gravity always points down into the ground (if you are not in space).
Another equation that says something about gravity is:
formula_2 is force; formula_13 is the gravitational constant, which is used to show how gravity accelerates an object; formula_14 is the mass of one object; formula_15 is the mass of the second object; and formula_16 is the distance between the objects.
This equation is used to calculate how the earth moves around the sun and how the moon moves around the earth. It is also used to calculate how other planets, stars and objects in space move around.
The equation says that if two objects are very heavy then there is a strong force between them because of gravity.
If they are very far apart then the force is weaker.
Laboratory techniques
Laboratory techniques are the techniques of handling the various pieces of apparatus.
Ways to dissolve a solid in a liquid or to mix two liquids in a test tube:
International System of Units
The International System of Units is the standard modern form of the metric system. The name of this system can be shortened or abbreviated to SI, from the French name "Système International d'unités".
The International System of Units is a system of measurement based on 7 base units: the metre (length), kilogram (mass), second (time), ampere (electric current), Kelvin (temperature), mole (quantity), and candela (brightness). These base units can be used in combination with each other. This creates "SI derived units", which can be used to describe other quantities, such as volume, energy, pressure, and velocity.
The system is used almost globally. Only Myanmar, Liberia, and the United States do not use SI as their official system of measurement. In these countries, though, SI is commonly used in science and medicine.
The metric system was created in France after the French Revolution in 1789. The original system only had two standard units, the kilogram and the metre. The metric system became popular amongst scientists.
In the 1860s, James Clerk Maxwell and William Thomson (later known as Lord Kelvin) suggested a system with three base units - length, mass, and time. Other units would be derived from those three base units. Later, this suggestion would be used to create the centimetre-gram-second system of units (CGS), which used the centimetre as the base unit for length, the gram as the base unit for mass, and the second as the base unit for time. It also added the dyne as the base unit for force and the erg as the base unit for energy.
As scientists studied electricity and magnetism, they realized other base units were needed to describe these subjects. By the middle of the 20th century, many different versions of the metric system were being used. This was very confusing.
In 1954, the 9th General Conference on Weights and Measures (CGPM) created the first version of the International System of Units. The six base units that they used were the metre, kilogram, second, ampere, Kelvin, and candela. The seventh base unit, the mole, was added in 1971.
SI is now used almost everywhere in the world, except in the United States, Liberia and Myanmar, where the older imperial units are still widely used. Other countries, most of them historically related to the British Empire, are slowly replacing the old imperial system with the metric system or using both systems at the same time.
The SI base units are measurements used by scientists and other people around the world. All the other units can be written by combining these seven base units in different ways. These other units are called "derived units".
Derived units are created by combining the base units. The base units can be divided, multiplied, or raised to powers. Some derived units have special names. Usually these were created to make calculations simpler.
Very large or very small measurements can be written using prefixes. Prefixes are added to the beginning of the unit to make a new unit. For example, the prefix "kilo-" means "1000" times the original unit and the prefix "milli-" means "0.001" times the original unit. So one "kilometre" is 1000 metres and one "milligram" is a 1000th of a gram.
Lake Michigan
Lake Michigan is one of the five Great Lakes in North America. It has a surface area of . It is wide. Lake Michigan is the 5th largest lake in the world.
Lake Michigan is surrounded by the U.S. states of Indiana, Illinois, Wisconsin, and Michigan. It is the only Great Lake that is not partly in Canada. The largest city on the shore of Lake Michigan is Chicago.
The earliest time that people lived near the lake was 800 CE. The word "Michigan" originally meant the lake itself. It is believed to come from the Ojibwa word "mishigami" meaning "great water".
The first person to reach the deepest part of Lake Michigan was J. Val Klump. Klump reached the bottom with a submarine as part of a 1985 research expedition.
Twelve million people live along Lake Michigan's shores. They are mainly in the Chicago and Milwaukee areas.
Gas syringe
A gas syringe is a tool used in a laboratory. It is used to collect a gas or to measure the volume of a gas.
Simple systems can be settled in the laboratory to collect gas or to compress it. It is usually used to explain Gas Law.
Mixture
In chemistry, a mixture is a substance that is made up of two or more simpler substances. These substances can be chemical elements or compounds. A mixture can be made of liquids, solids, or gases.