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Miscellaneous Forces. Weight. Weight is the force of gravity upon an object. This force is represented by the symbol F g (units of Newtons) Acceleration of gravity on the earth is always -9.81 m/s/s, so weight can be calculated by multiplying the mass and -9.81 m/s/s. Normal Force.
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Weight • Weight is the force of gravity upon an object. This force is represented by the symbol Fg (units of Newtons) • Acceleration of gravity on the earth is always -9.81 m/s/s, so weight can be calculated by multiplying the mass and -9.81 m/s/s
Normal Force • Normal Force is the force of a surface on an object, and acts against the force of gravity (weight). It is always perpendicular to the contact surface. It is represented by Fn
Force of Friction • Friction is a force that opposes applied force • Static friction is the force that is exerted on a motionless object, and is always equal but opposite to an applied force. It is represented by Fs. • There is a limit where the static friction can no longer keep the object motionless. This limit is called the Fs,max
Force of Friction • Kinetic friction is the force that opposes motion of a moving object. It is a fixed amount that depends on the surfaces involved. It is represented by the symbol Fk
Force of Friction • The coefficient of friction describes the relative amount of friction between two surfaces. It is represented by μs or μk • It can be calculated by: μs= Fs,max / Fn • μk = Fk / Fn • See page 102 for a table of values