A pendulum swings through an arc length of 1120 cm (Swing #1). With each further swing, the arc length is reduced by 15 %

Question

State the growth factor.

Calculate the length of the arc in swing #5

I think im supposed to use this formula again, but I don't know how to use it. Tn = ar^n-1

Answer 1

swing #1 : 1120
swing#2: 1120(.85) = 952
swing #3 : 952(.85) or 1120(.85)^2 = 809.2
..
swing#5 = 1120(.85)^4 = 584.647 cm

Answer 2

Where did you get 0.85 from?

Answer 3

100% - 15% = 85% = .85

Answer 4

Ok wait, sorry sorry. I actually messed writing the question. Its supposed to be 120 cm, not 1120 cm. But you're still right, the growth factor is 0.85m but I don't know how you got that:\

Answer 5

swing#5 = 120(.85)^4 = 63?

Answer 6

yes, to the nearest cm , I had 62.64

Answer 7

But I checked the answer, and it says its 73.695 :S

Answer 8

Ok, maybe I messed up writing the whole thing, I'll rewrite it again.

A pendulum swings through an arc of 120 cm (Swing #1)
With each further swing, the arc length is reduced by 15%

State the growth factor

Calculate the length of the arc in Swing #4

Answer 9

Their answer is wrong.

According to your typing

swing#1 = 120
swing #2 = 120(.85) =
swing#3 = 120(.85)^2
swing #4 = 120(.85)^3 = 73.695
swing#5 = 120(.85)^4 = 62.64

Their answer would be for the 4th swing.

Answer 10

Oh ok, thanks so much, it was all because of my typing mistake :S Sorry about that.