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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
