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# questions about centrifugal force and newtons law...

Posted in the Physics Forum

d_out
#1 Sep 7, 2011
i was looking up about centrifugal force and the relations, speed of rotation, and radius from center. so wouldn't there be something to do with newtons law if a weight was extended(basically circular or rotation), had a constant speed but a radius that changed as the weight would go around. i did a little math on this:

F = mV^2/R.

A 0.8 kilogram mass on the end of a 1.5 meter string is traveling at 9 meters per second. The force that must be exerted on the string to hold on to the mass is given by 0.8 x 9^2 / 1.5 = 43.2 newtons.

the centrifugal force w/ fixed radius is constant if speed of rotation is constant, then if radius is varied and speed of rotation is constant, then the forces on the weight(spinning) would also be changing as the radius changed.

if the weight was on shorter radius at 0' rotation and at longer radius at 180' as the weight rotated about a center wouldn't newtons laws say that the differing of centrifugal force would cause some movement.

the math reveals a sizable difference in the amount of newtons exerted to the weight per change of radius, forces vary with rpm.

Since: Jul 11

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#2 Sep 17, 2011
d_out wrote:
i was looking up about centrifugal force and the relations, speed of rotation, and radius from center. so wouldn't there be something to do with newtons law if a weight was extended(basically circular or rotation), had a constant speed but a radius that changed as the weight would go around. i did a little math on this:
F = mV^2/R.
A 0.8 kilogram mass on the end of a 1.5 meter string is traveling at 9 meters per second. The force that must be exerted on the string to hold on to the mass is given by 0.8 x 9^2 / 1.5 = 43.2 newtons.
the centrifugal force w/ fixed radius is constant if speed of rotation is constant, then if radius is varied and speed of rotation is constant, then the forces on the weight(spinning) would also be changing as the radius changed.
if the weight was on shorter radius at 0' rotation and at longer radius at 180' as the weight rotated about a center wouldn't newtons laws say that the differing of centrifugal force would cause some movement.
the math reveals a sizable difference in the amount of newtons exerted to the weight per change of radius, forces vary with rpm.
Haven't read carefully, but -have you incorporated Coriolis in the equation ? If so- what's the contention ?

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