Ch. 3 Forces

Friction

force that opposes the sliding motion of two surfaces that are touching each other

Microwelds

are the source of friction

Static friction

frictional force that prevents two surfaces from sliding past each other

Sliding friction

force that opposes the motion of two surfaces sliding past each other; sliding friction is caused by microwelds constantly breaking and then forming again as the object slides along the floor

Rolling Friction

frictional force between rolling objects and the surface it rolls on

Air resistance

a friction-like force, opposes the motion of objects that move through the air

Gravity

an attractive force between any two object that depends on the masses of the objects and the distance between them; this force increases as the mass of either object increases or as the objects move closer

G is a constant called the universal gravitational constant, and d is the distance between the two masses

m1 and m2

Weight

the gravitational force exerted on an object

Centripetal acceleration

the acceleration toward the center of a curved or circular path

Centripetal force

the net force exerted toward the center of a curved path

Momentum

of an object is the product of its mass and velocity

Momentums equation

p = mv

Since acceleration is the difference between the initial and final velocity divided by the time, and due to the second law of motion

the net force on an object equals its mass times it acceleration

When you combine these two concepts you get Newtons second law written like this

F =( mvf−mvi)/t

The momentum of an object is the product of its mass and velocity

p = mv

The force of gravity on an object with mass, m, is

F = mg

The weight of an object near Earths surface is

W = mg