# SHM question

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#1
The amplitude of an oscillating mass on a spring decreases by 4% each cycle from an initial amplitude of 100mm. Calculate the amplitude after 20 cycles of oscillation.
0
1 year ago
#2
I like turtles.
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#3
(Original post by goggleyed)
I like turtles.
What kind of turtles tho? Could you help me out with the question plsss?
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1 year ago
#4
is that physics?
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1 year ago
#5
(Original post by onionnn)
What kind of turtles tho? Could you help me out with the question plsss?
sorry lad i could barely understand the question hence my response. just pointing out that i'm a complete simpleton
1
1 year ago
#6
(Original post by onionnn)
The amplitude of an oscillating mass on a spring decreases by 4% each cycle from an initial amplitude of 100mm. Calculate the amplitude after 20 cycles of oscillation.

You can start the problem by writing:
After 1st cycle, the amplitude A1 is
A1 = 0.96A0

After 2nd cycle, the amplitude A2 is
A2 = 0.96A1

After 3rd cycle, the amplitude A3 is
A3 = 0.96A2

….

Till 20th cycle….

This problem is like “compound interest” problem in a reverse manner.
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1 year ago
#7
(Original post by onionnn)
I just thought there would be a more efficient way to do it
Yeah, can you think of how to do those steps all in one go?
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#8
(Original post by K-Man_PhysCheM)
Yeah, can you think of how to do those steps all in one go?
Omg yeah forgot there's an equation for compound interest
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1 year ago
#9
(Original post by onionnn)
Omg yeah forgot there's an equation for compound interest
Well sure but you don't need to memorise the equation, just think about how many times you need to multiply the amplitude by the scale factor (0.96 in this case).
After one oscillation, the amplitude is 0.96*A
After two oscillations, the amplitude is (0.96^2)*A
After three oscillations, the amplitude is (0.96^3)*A

so what's the amplitude after 20 oscillations? No need to memorise a formula, just think about what's going on
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