Sound Experiments

Question 1

How were tension and length measured in terms of diagram in the experiment variation of fundamental frequency of stretched string with tension

Answer 1

Tension was read off Newton Balance. Length was measured from top of one bridge to the other

Question 2

How would you draw a graph in the experiment variation of fundamental frequency of stretched string with tension

Answer 2

Manipulate data for graphing and calculate square root T.

Plot graph with frequency on y-axis and square root of tension on x-axis.

Question 3

How would a graph verify the relationship between F and T in the experiment variation of fundamental frequency of stretched string with tension

Answer 3

A straight line through the origin verifies that frequency is proportional to the square root of the tension

Question 4

How was the fundamental frequency determined

in the experiment variation of fundamental frequency of stretched string with tension

Answer 4

Move bridges till wire is about 1/3 of it’s max length
Strike tuning fork of lowest frequency and place it’s stem on a bridge.
Adjust tension until resonance occurs and paper rider is thrown off string.
Record tension and frequency of fork.
Repeat with other tuning forks recording their frequency and corresponding tension value that caused resonance.

Question 5

How do you know resonance occurred in the experiment variation of fundamental frequency of stretched string with tension?

Answer 5

Paper rider is thrown off the string

Question 6

How do you draw graph of data in the experiment variation of fundamental frequency of stretched string with length?

Answer 6

Manipulate data for graphing and calculate 1/l

Plot graph with frequency on y-axis and the reciprocal of length on x-axis.

Question 7

State the relationship between f and l and how it is verified by graph in the experiment variation of fundamental frequency of stretched string with length

Answer 7

f is proportional to 1/l

Straight line graph through the origin confirms this.

Question 8

How was data obtained in the experiment variation of fundamental frequency of stretched string with length

Answer 8

Make wire as long as possible
Strike tuning fork of lowest frequency and place stem on bridge.
Adjust tension until resonance occurs and then measure and record l
Keep tension like this for the rest of experiment
Strike tuning fork of next highest frequency and place stem on bridge
Adjust length moving bridges until resonance occurs and paper is thrown off wire.
Note and record l and frequency of fork
Repeat with remaining tuning forks recording corresponding lengths of string when resonance occurs

Question 9

Apart from length give the relationship between f and another factor it depends on

Answer 9

f is proportional to square root T or square root 1/mass per unit length

Question 10

Write and expression for mass per unit length in terms of T and slope in the experiment variation of fundamental frequency of stretched string with length

Answer 10

Slope of graph +f / 1/l or f x l

So square both sides of f =(1/2l)(square root of T/mass per unit length) to get f^2 = T/4l^2 x mass per unit length

this means mass per unit length = T/4l^2 x f^2

Which is the same as T/4(lxf)^2

Replace (l x f) with m and so mass per unit length= T/4m^2

Question 11

Write and expression for mass per unit length in terms of l and slope in the experiment variation of fundamental frequency of stretched string with tension

Answer 11

Slope of graph m=f/square root T

So square both sides of f =(1/2l)(square root of T/mass per unit length) to get f^2 = T/4l^2 x mass per unit length

this means mass per unit length = 1/4l^2 x T/f^2

Replace T/f^2 because (m^2 = f^2/T and 1/m^2 = T/f^2)

So mass per unit length = 1/4l^2m^2

Question 12

How was first position of resonance found in the experiment to measure the speed of sound in air with resonance tube?

Answer 12

Set up apparatus
Strike highest frequency tuning fork and place over open end of tubing
Raise inner tube and adjust to find length with max loudness
First resonance point- frequency of vibrating air column is the same as fork
Measure and record l
Note and record tuning fork frequency
Repeat with other tuning forks.
Measure internal diameter with sliding callipers

Question 13

What is wavelength equal to (formula) in the experiment to measure the speed of sound in air with resonance tube?

Answer 13

wavelength = 4(l+d)

d is end correction aka 0.3 x diameter

Question 14

Why do you need to measure the diameter in the experiment to measure the speed of sound in air with resonance tube?

Answer 14

Takes into account the gap between the tuning fork and the end of tubing. The vibrating column air extends a little beyond end of tube

Question 15

How is speed of sound in air calculated in the experiment to measure the speed of sound in air with resonance tube?

Answer 15

c = f x 4(l+d) 
d= end correction aka 0.3 x diameter

Calculate for each recording and find average

Question 16

Describe how diameter was measured in the experiment to measure the speed of sound in air with resonance tube?

Answer 16

Measure internal diameter with sliding callipers

Question 17

Describe how frequency of column of air was measured in the experiment to measure the speed of sound in air with resonance tube?

Answer 17

Read off tuning fork

Question 18

Describe how length of column of air was adjusted in the experiment to measure the speed of sound in air with resonance tube?

Answer 18

Inner tube was raised up and down- length was distance from top of outer tube to top of inner tube

Question 19

How was it known the air column was vibrating at its first harmonic in the experiment to measure the speed of sound in air with resonance tube?

Answer 19

First time resonance occurred and loud sound was heard as tube was raised

Question 20

How do you find speed of sound without diameter?- first two positions of resonance in the experiment to measure the speed of sound in air with resonance tube?

Answer 20

Well for length 1
wavelength/4= (length 1 +d)

For length 2
3 x wavelength/4 =(length 2+d)
Subtract these to get that wavelength/2 = length 2 - length 1 so wavelength = 2(l2 - l1)

therefore c = fx2(l2-l1)

Question 21

How is data handled for graphing in the experiment to measure the speed of sound in air with resonance tube?

Answer 21

Plot graph of l on y-axis and 1/f on x-axis.

Straight line graph will result and slope of graph is equal to speed of sound /4

Question 22

How can speed of sound be found with slope of graph in the experiment to measure the speed of sound in air with resonance tube?

Answer 22

Slope x 4 = speed of sound in air

Question 23

Give three things to note on the accuracy of experiment to measure the speed of sound in air with resonance tube?

Answer 23

Errors can arise in locating position of loudest sound
Avoid error of parallax with metre stick
Avoid tuning forks of high frequency as they correspond to small values for length resulting in higher percentage error