Forces and Uniform Circular Motion
Note ­ Centripetal acceleration refers to an object experiencing uniform circular motion. Centrifugal motion is an incorrect concepts. The object wants to fly straight because of ________________, not an outward force.
So, the net force associated with uniform circular motion is called the ___________________ ___________.
Note ­ the centripetal force is the net force not an Fi
ƩFi = Fnet = ma
Hwk pg 111 1­3, 5­7
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Centripetal Force Lab
Purpose: To verify the equation for centripetal force Fc = mv2/R
Introduction : Centripetal acceleration results when an object travels with uniform circular motion ­ that is with a constant speed in a circle. The direction of the acceleration is always inward. An inward force is required to prevent the object from travelling in a straight line and thus the acceleration is also inward.
To measure the centripetal force on an object, one has to create a situation where some measurable force can be argued as the only force exerted on the spinning mass. We will use the following set­
up.
The argument is that the only force on the rubber stopper rotating is the Tension in the rope. This tension, an action reaction force, is created by the force of gravity on the washers. Therefore, one can compare determine the Tension from the force of gravity and compare it to the measured and calculated centripetal of the washer.
ƩFi=Fnet=mac
T1 = mwashersg
T2 = mstopperv2/R
Therefore to verify the centripetal force equation we must determine, with this apparatus, how close T1 and T2 are. Note ­ we cannot state T1 = T2 if we are trying to show they are equal and we should know with measurement uncertainty, that a true equality will not be obtained.
Note ­ as the angle increases, a component of the Tension is spent to offset the force of gravity on the stopper. This angle has to be controlled as much as possible.
Variables to measure ­ mass (2), radius, and Period
Independent variable
Dependent variable
Controls 4