TYPES OF FORCES AND FRICTION

Forces

A force is a push or a pull that acts on an object

A force can cause a resting object to move or it can accelerate a moving object by changing the object’s speed or direction

Example wind

Measuring ForceThe unit of force is a newtonA newton causes one kilogram of mass

to accelerate at a rate of 1 meter per second, each second

1N = 1 kg*m/s2

Named after Sir Isaac Newton(much different than fig newtons)

1. Adding Forces + =

2.Subtracting Forces=

3.Equal and opposite forces= 0

Friction

Friction is a force that opposes the motion of objects that touch as they move past each other

Without friction walking would be impossible, cars would slide around helplessly

Static Friction is the friction force that acts on objects that are not moving

Example you are trying to push a potted plant but can not move it, static friction is working against you

Each time you step you experience static friction between the ground and your shoe

Sliding FrictionSliding friction is a force that opposes the

direction of motion of an object as it slides over a surface

It is less than static frictionAs the flower pot is moving there is less

friction so it takes less force to move it

Rolling Friction

The friction force that acts on rolling objectsIt is about 100 to 1000 times less than static

or sliding frictionExample ball bearings used to reduce friction

in machines

Fluid FrictionThe forces that opposes the

motion of an object through a fluidYou would feel this friction when

you are stirring cake batterFluid friction increases as the

speed of the object increases

Fluid Friction cont.Fluid friction acting on an object

through the air is known as air resistance

Bicyclists and speed skaters will wear slick racing suits to reduce air resistance