Resistance defines friction. Friction consists of the resistance of one object in relation to another object with which it is in contact. Thus, friction is the force that opposes sliding motion, explains the Cornell Center for Materials Research. An example of friction involves removing a stain from clothing. You place detergent on a stained shirt, then repeatedly slide part of the shirt against the stained section. The friction eliminates the stain from the shirt.
Gravity
Gravity is simply defined as what goes up must come down. Gravity is the natural force exerted between two objects, drawing them toward each other. Therefore, instead of an object such as an apple thrown in the air staying there or floating, it falls down. Weight is extremely important to gravity. Gravity always exerts a force equal to the weight of the object it is acting on. A cup remains on a table because the upward force of the table is equal to the weight of the cup, causing it to stay in place.
