Pendulum Altitude
Date: 09/26/2002 at 06:43:45
From: Relle
Subject: Trigonometry
This question is related to Trigonometry.
A pendulum 45cm long swings through a vertical angle of 30 degrees.
Find the distance of the altitude through which the pendulum bob
rises. (Answer: 1.533cm)
I have problems drawing (visualising) this picture, and am thus unable
to solve this problem. Maybe if you could try to include a picture
I'll be able to understand the answer better. Thanks.
Date: 09/26/2002 at 09:17:52
From: Doctor Ian
Subject: Re: Trigonometry
Hi Relle,
Here is a diagram of the situation:
A
/|\
/ | \ AP = AP' = AP"
/ | \
/ | \
P' | P"
P
It's not clear which of the following is the case:
1) angle P'AP" = 30 degrees
2) angle PAP" = 30 degrees
I'll leave that for you to work out with your teacher. In either case,
it's angle PAP" that you're interested in. Let's look more closely at
that:
A
|\
| \
| \
| \
| \ AC is vertical
| \ CP" is horizontal
| \ therefore angle ACP" = 90 degrees
C.......P"
|
P
Now, note that
length of AC
cos(PAP") = ------------
l ength of AP"
Can you take it from here? If you're having trouble following what I
did, you might want to take a look at
