Applied Force (Fapp) – An applied force is the force that a person applies to an object. It is any push or pull caused by a person.
Weight (FG) – The weight of an object measures how heavy it is. It is caused by earth’s gravity pulling on the object. It can be calculated using the mass of the object: FG = mg
Normal Force (FN) – The normal force is the force of a surface pushing back against an object. It measures how much a surface (like the ground or a table) must push back to support the weight of an object. For example, if you place a 2 lb book on a table, the table must push up on the book with a force of 2 lbs in order to support the weight.
Tension (FT) – Tension is a force that is being applied by a rope, cable, or string.
Friction (Ff) – Friction is a force that always opposes motion. It is caused when two rough surfaces scrape against each other. Even surfaces that seem very smooth have friction because of microscopic bumps and cracks on its surface. It can be calculated using the normal force: Ff = μ FN. The symbol “μ” is the coefficient of friction. It measures how rough the surface is; the larger the coefficient, the rougher the surface.