Amplitude and intensity of rock concert

  • Thread starter L1988
  • Start date
  • #1
11
0

Homework Statement



At a rock concert, the engineer decides that the music isn't loud enough. He turns up the amplifiers so that the amplitude of the sound, where you're sitting, increases by 87.0%. By what percentage does the intensity increase? Do not enter unit.

Homework Equations




I used the fact that intensity is proportional to amplitude squared.

(A2/A1)^2 = I2/I1


The Attempt at a Solution



85% increase in A, so:

(1.85)^2=I2/I1

3.4225=I2/I1

I2=3.4225I1

3.4225x100= 342%

342%-100% = 242%

Answer=242 <-- which is incorrect.

where did I make my mistake?
 

Answers and Replies

  • #2
140
0
Hey there,

For a start is it 87% or 85%?

L1988 said:
..increases by 87.0%
L1988 said:
..85% increase in A, so:
 
Last edited:
  • #3
4
0
the problem is that you didn't compute the percent by using a percent difference. All of your work is right but you need to use (I1-I2)/I1 = percent difference, use this instead of a straight fraction like you calculated. if you use this equation you will get the desired answer.
 

Related Threads on Amplitude and intensity of rock concert

Replies
2
Views
1K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
8
Views
2K
Replies
1
Views
14K
Replies
2
Views
4K
Replies
4
Views
4K
Top