O friction it is a type of force that is present when two surfaces come into contact. When we walk, we push the ground backwards, and the friction between our feet and the surface is responsible for propelling us forward. When rubbing your hands, you may feel heat because of the friction generated by the movement. Friction forces can be opposed to the movements, making them difficult, or in favor of the movements, when they facilitate their execution.
Mind Map: Friction Force
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Determination of friction force
The friction force is determined from the Normal force and a quantity called coefficient of friction (μ). A Normal is a force that acts vertically and upward on every object deposited on a surface. The friction coefficient is a dimensionless quantity that characterizes the surface that houses the object. The greater the value of this magnitude, the greater the resistance generated by the surface on the object and vice versa. By definition, friction force can be measured from the product of Normal by the friction coefficient:
FAT = µ.N
static friction
Static frictional force is the force that must be overcome in order for an object's movement to be possible. Imagine that you have tried to push a car that has broken down and that, despite all your effort, the vehicle has not moved. This is because the force applied to the car is less than the friction force existing between the tires and the ground.
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Dynamic Friction
Upon overcoming the force of static friction, movement occurs; however, the constant application of an external force is necessary, otherwise the movement will cease. Now the force made by an external agent is greater than the friction, which does not cease to exist, but is now called dynamic friction.
air resistance force
THE air resistance force it is a consequence of the interaction between air and the surface of a moving object. The determination of this resistance depends on the orthogonal area (A) of the moving object, velocity (v), density (d) of the air and a number called the drag coefficient (cTHE), which determines whether the moving body is very or very aerodynamic. The equation below measures the air resistance force (RAIR):
RAIR = ½ cTHE.d. AV2
The format that is considered to be the most aerodynamic is the drop of water, which has a very small drag coefficient value.
The drop shape would be ideal for cars as it would not cause turbulence in the rear of the car and would make moving around easier. In this aspect, the cars sedans stand out compared to the model hatch, that do not have an elongated back.
* Mind Map by Me. Rafael Helerbrock
By Joab Silas
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
JUNIOR, Joab Silas da Silva. "What is friction force?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-forca-atrito.htm. Accessed on June 28, 2021.
