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# Algebra 2 help please?!?

the period of a pendulum is the time the pendulum takes to swing back and forth. the function l=0.81(squared) relates the length l in feet of the pendulum to the period l.

A. If a pendulum is 30 feet long, what is the period of the pendulum in seconds?

B. why does only one of the solutions work for this problem?

the variables are all L

### 2 Answers

- Anonymous9 years agoFavorite Answer
T= 2*Pi*(L/g)^(1/2)

A. This means that if the pendulum is 30 ft. long the solution is about 6 seconds to oscillate.

B. Since L is the only variable that is present, (g is gravity) there can only be one answer for when one lenght is given.

This is a correct answer. I am not sure how you can relate L=.81^2 to L. There are no variables.

- Ian HLv 79 years ago
You can do easy questions like this if you just concentrate and try properly.

Probably it seemed harder because you missed a bit when you copied the question.

It should have been

L = 0.81*T^2 (otherwise it makes no sense).

A. There is no mystery to this, you hardly have anything to do,

just put 30 where it said L and you get

30 = 0.81*T^2

rearrange to find T

(remembering that a square root has two solutions one positive and one negative)

T = sqrt(30/0.81) ~ 6.086 or -6.086

B. Since time only goes forward a period of about minus 6 seconds

does not make much sense so only the positive solution works.

Now I hope you see how easy it was.

Regards - Ian