Unformatted text preview: sure the frequency is be using the spring constant. We know that
the frequency is related to the spring constant as 1
2 (68) However for this experiment, we have two spring and thus two spring constants. Thus we must write the
total spring constant k (See Figure 11) as (69)
Therefore equation (68) becomes 1
2 (70)
12 4.2 Simple Pendulum
For the second part of this experiment, you
will measure the period of a simple pendulum. You
will then use the period to calculate the frequency of
the simple pendulum and compare that value to the
theoretical value predicted using the small angle
approximation. We know that the frequency is related
to the period as Figure 11 Diagram of mass attached to two strings. This
is similar to the experiment that you will be performing.
http://scienceworld.wolfram.com/physics/SpringsTwoSpr
ingsandaMass.html 1 (71) You can see that the frequency is simply just the inverse of the period and vice versa. Once you measure
the period you will use the small angle approximation of the simple pendulum 1
2 (72) Once you calculate the frequency, you will then find the % Difference of the frequency predicted by
equation (65) and the one measured using equation (71).
Now that you have the theoretical value for the frequency, you will notice that it involves gravity.
Thus we can measure gravity by knowing the frequency and the length of the pendulum. Thus we can
find gravity using 2 (73) For the final part of the calculation of the simple pendulum you will find the acceleration of gravity using
the frequency that you measured and putting this into equation (73).
4.3 Physical Pendulum
The final thing that you will do in the lab, is measure the frequency of a physical pendulum so
the first measure the length of the rod L, the rod mass MR, and the mass of the brass (bob) MM. We will
start with the predicted frequency of a physical pendulum which is given by 1
2 (74) where M is the total mass of the pendulum, h is the distance from the pivot point to the centerofmass of
the pendulum, and I is the rotational inertia of a thin rod about its end. From Table 1 of the angular
motion lab, we know tha...
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 Fall '09
 Mass, Simple Harmonic Motion, Rotary Motion Sensor

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