ESS229
Prof. Jin-Yi Yu
Centrifugal Force
• An
observer ( ) in an inertial
coordinate
èsees the ball’s direction keeps on
changing
è there is a centripetal force applied to the
ball
• Acceleration of the ball = (δV / δt)
è and in the limit
of
è (“-”:
force goes inward)
è because
è = -(V2/r)
è The ball is pulled inward by the
centripetal force
A ball of mass m is attached to a string and whirled through a
circle of radius r
at
a constant angular velocity ω.
• An
observer ( ) rotating with the
ball
è sees no change in the ball’s motion
è but the observer sees the pulling of the ball
by the string
è in order to apply Newton’s 2nd law to describe the ball’s motion in this
rotation coordinate
è an apparent force has to be added which is
opposite to centripetal force
è centrifugal force = - centripetal force =
