Common Forces

Units

F = ma m is measured in kg a is measured in m/s2

F is measured in kg m/s2, called a Newton (N)

Gravity (Fg)

Acts at a distance (gravitational field)

Force due to Gravity = Weight Acceleration due to Gravity =

Constant g = 9.8 m/s2

Normal Force (FN)

Contact Force Acts perpendicular to the surface

Friction (Ff)

Contact force

Acts parallel to the surface

Acts opposite the direction of motion

Spring Force (Fs)

Contact force Acts opposite the

direction the spring is stretched or compressed

Proportional to stiffness of spring and how much it is stretched or compressed

Tension (T)

Contact force Force exerted by a

string or rope Always acts along the

string or rope Equal on both ends of

the string or rope** Unless you have a pulley with mass, like in AP Physics