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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