Download Centripetal and Gravitational Forces

Centripetal Force and Centrifugal
Force. Newton's Universal Law of
Gravitation
By Corina Bot
Centripetal Force - The Real Force
• cars are forced through a loop by
the track applying a centripetal force
on them.
• The reactive centrifugal force of
the cars, associated with their inertia,
holds them on the track
http://sciencefair.math.iit.edu
Centripetal Force - The Real Force
Definition:
Centripetal  Latin for "center seeking“
Centripetal force is a center seeking force => the force is
always directed toward the center of the circle and orthogonal to
the velocity of the body.
From Newton’s 2nd law
Using centripetal acceleration definition
We have centripetal force
F  m  ac
v2
ac 
r
2
mv
F
r
Centripetal Force - The Real Force – Examples:
mv
F
r
2
• The smaller the velocity of the object, the less centripetal force you will have to
apply.
• The smaller the length of rope (radius), the more centripetal force you will have to
apply to the rope.
• Notice that the centripetal force and the centripetal acceleration are always pointing
in the same direction.
http://regentsprep.org
Centrifugal Force – The False Force
Definition:
Centrifugal  Latin for "center fleeing“
Centrifugal force ("fictitious" force) represents the effects of inertia that arise
in connection with rotation
 It is experienced as an outward force away from the center of rotation.
Centrifugal force example - cars driving on a wall
http://en.wikipedia.org
Newton's law of universal gravitation
• Every point mass attracts every other point mass by a force pointing
along the line intersecting both points.
• The force is directly proportional to the product of the two masses
and inversely proportional to the square of the distance between the
point masses.
F = the magnitude of the gravitational force between the two point masses,
G = the gravitational constant,
m1 = the mass of the first point mass,
m2 = the mass of the second point mass, and
r = the distance between the two point masses.
http://en.wikipedia.org