This preview shows pages 1–2. Sign up to view the full content.
Physics 1240
Homework 1 solutions
Brief solutions to homework set #1. Your numbers will be diﬀerent, but the idea is the same.
I’m just using sample numbers here.
1. The graph below represents the function
Y
=
ax
. Make a graphical estimate of the value of
a
.
Here the key idea is that the slope
a
, is the change in
Y
divided by the change in
x
(the
“rise” over the “run”). Reading oﬀ the graph, for this example
Y
increased from 0 to about
11 when
x
changed from 0 to 2, giving a slope
a
≈
5
.
5.
2. Because Boulder is above sea level, normal atmospheric pressure is not 1 atm. Suppose the
atmospheric pressure is 0.850 atm on a given day. If the rarefactions of a particular sound
wave then reduce the pressure to 0.846 atm, what is the amplitude of the pressure wave? Is
this a loud sound or a soft sound? How do you decide?
The underpressure is 0.850  0.846 atm = 0.004 atm, which is the same as the amplitude of
the pressure wave. To convert this to Pa, use the conversion that 1 atm = 1
.
013
×
10
5
Pa, so
we have
0
.
004 atm
×
1
.
013
×
10
5
Pa
1 atm
= 405
.
2 Pa
.
In class and in the reading, we discussed an example of a sound with an amplitude of 1
Pa, and explained that this pressure corresponds to a loud but normal sound. Your ear is
a very sensitive detector, capable of hearing pressure variations of only 1 part in 10
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 HOLLAND,MURRAY
 Work

Click to edit the document details