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M o d e l N o . M E - 9 5 0 2 E x p . 1 1 A : S i m p l e H a r m o n i c M o t i o n – P h y s i c a l P e n d u l u m
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2. Does the equation for the theoretical period of this physical pendulum provide a good mathematical model for
the physical reality? Why or why not?
Try This
• If you assume that the distance L
cm
from the pivot point to the center of mass is L /2, exactly half the length of
the rod, then the formula for I
parallel
gives a simpler expression:
• Substituting this expression into the formula for the period of oscillation of a physical pendulum gives:
• Use this expression to re-calculate the theoretical period of the physical pendulum and compare the result to
the measured period of oscillation.
• How much difference is there between the re-calculated theoretical period and the previous theoretical
period?
I
parallel
I
cm
mL
cm
2
+
1
12
------
mL
2
mL
cm
2
+
1
12
------
mL
2
m
L
2
---
 
 
2
+
1
12
------
mL
2
1
4
---
mL
2
+
1
3
---
mL
2
= = = = =
T 2

I
parallel
L
cm
mg
-------------------- 2

1
3
---
mL
2
L
cm
mg
----------------- 2

1
3
---
mL
2
L
2
---
mg
-------------- 2

2 L
3 g
------ = = = =