Friction and pressure
Physics
Frictional force
• Friction acts on
materials that are in
contact with one
another
• Friction is caused by
irregularities in the
two surfaces
• meter stick demo
friction
The force of friction depends on:
• Kinds of material
• how much the surfaces are
pressed together
• Friction does not depend
on the amount of surface
area in contact
• friction turns mechanical
energy into heat
• heat demo(fire drill)
Friction occurs in liquid and gas
• Liquids and gas are
called fluids (because
they flow)
• air resistance is a
common form of fluid
friction
Is it possible to move at a
constant velocity:
• Even when a force is
applied?
• terminal velocity ( no
acceleration)
A free body diagram:
• Shows all the forces
acting on an object
Pressure
• Pressure = force / area
• The bigger the area the
less force
• Smaller the area the
more force
• ice skater
• knife blade
Atmospheric pressure
• Atmospheric pressure
is 10.13 N/cm2
• Egg in the bottle demo
• Shrink wrap demo