Transcript Centripetal Force

Centripetal Force
Key Question:
Why does a roller coaster stay on a track
upside down on a loop?
Centripetal Force
• Any force that causes an object to move in a
circle is called a centripetal force.
• A centripetal force is always perpendicular to
an object’s motion, toward the center of the
circle.
Centripetal Force
Mass (kg)
Centripetal
force (N)
Fc = mv2
r
Linear speed
(m/sec)
Radius of path
(m)
Calculate centripetal force
• A 50.0-kg passenger on an amusement park
ride stands with his back against the wall of a
cylindrical room with radius of 3.0 m. What is
the centripetal force of the wall pressing into
his back when the room spins and he is
moving at 3.0 m/s?
Centripetal Force
Centripetal
force (N)
Mass (kg)
Radius of path
(m)
2
Fc = m4π r
T2
period
(sec)
Centripetal Force
Mass (kg)
Centripetal
force (N)
Fc = m4π2rf2
frequency
(Hz)
Radius of path
(m)
Centrifugal Force
• We call an object’s tendency to resist a change in its motion
its inertia.
• An object moving in a circle is constantly changing its
direction of motion.
• Although the centripetal force pushes you toward the center
of the circular path...it seems as if there also is a force pushing
you to the outside. This apparent outward force is called
centrifugal force.
Centrifugal Force
• Centrifugal force is not a true force exerted on your
body.
• It is simply your tendency to move in a straight line
due to inertia.
• This is easy to observe by twirling a small object at
the end of a string.
• When the string is released, the object flies off in a
straight line tangent to the circle.