e.g RON RON frictional force

• frictional force- the force that opposes the motion of an object in contact with another object,another type of resistance force
• four kinds of friction- static,sliding,rolling,fluid
• static friction- when two surfaces are stationary relative to one another but there is still some force between them
• sliding friction- when two surfaces move past each other
• rolling friction- when something rolls along a surface
• fluid friction-occurs when an object's motion through water or gas have its resistance
• air resistance-happens when an object falls through the air.