Sound experiments

Question 1

speed of sound in air using a resonance tube - method

Answer 1

• set up as per diagram, hold resonance tube in clamp on retort stand.
• strike tuning fork of highest freq off striking block + hold above resonance tube.
• adjust length of column of air, l, by moving it further or less into the water. Do this until sound emitted is loud, this means resonance occurring.
• adjust l to get exact position of resonance, when sound at its loudest
• measure from top of water to top of tube using metre stick
• repeat for diff tuning forks of diff freqs
• measure internal diameter of tube using vernier callipers

Question 2

speed of sound in air using a resonance tube - graph

Answer 2

x-axis: 1/frequency (1/f) (Hz)

y-axis: length (m)

Question 3

variation of fundamental freq of a stretched string with length - method

Answer 3

• set up as per diagram
• strike lowest freq tuning fork off striking block, place stem on one of bridges
• adjust length until stretched wire resonates (paper rider falls off) with vibrating tuning fork
• tension remains constant
• measure the length between tops of two bridges using metre stick + record freq on tuning fork
• repeat with diff forks, but change the length to suit nex tuning fork

Question 4

variation of fundamental freq of a stretched string with length - graph

Answer 4

x-axis: 1/length (1/m)

y-axis: frequency (Hz)

Question 5

variation of fundamental freq of a stretched string with tension - method

Answer 5

• set up as per diagram
• strike lowest freq tuning fork off striking block, place stem on one of bridges
• adjust tension until stretched wire resonates (paper rider falls off) with vibrating tuning fork
• length must remain constant
• record tension off newton spring balance + freq of tuning fork
• repeat with diff forks, but change the tension to suit next tuning fork

Question 6

variation of fundamental freq of a stretched string with tension - graph

Answer 6

x-axis: √T (√N)

y-axis: frequency (Hz)

Question 7

freq with length - “indicate on your diagram the measured length of string”

Answer 7

draw an arrow labeled “l”/”length of string” between the tops of the two bridges in diagram

Question 8

freq with length - state the relationship + how graph verifies it

Answer 8

f ∝ 1/l

-straight line through origin

Question 9

freq with length - use graph to calculate length of string at a certain freq

Answer 9

• value read from graph eg. 1/l = 1.52m⁻¹

- invert value to get the length

Question 10

freq with length - use graph to calculate mass per unit length of string

Answer 10

use the fundamental freq formula

Question 11

freq with length - how data was obtained

Answer 11

• diagram, arranged as shown in diagram
• vibrating tuning fork placed on bridge
• adjust length until resonance occurs (paper rider falls)
• measure length between bridges
• repeat with forks of diff frequencies

Question 12

freq with length - if you were doing an experiment to establish the relationship between f and another factor, how would you obtain the data?

Answer 12

• find resonance for a fork by changing tension
• keep length fixed
• change + measure tension using Newton spring balance
• repeat for forks of diff frequencies

Question 13

freq with tension - show on diagram how tension and lengths were measured

Answer 13

• newton balance

- indicate where length was measured + include ruler

Question 14

freq with tension - how fundamental freq was determined

Answer 14

-adjust tension until resonance observed (paper rider falls off)

Question 15

freq with tension - how would a student use the measurements to draw a graph showing the relationship between freq and tension?

Answer 15

graph of f against √T

-sketch graph as well

Question 16

freq with tension - how graph verifies this relationship

Answer 16

straight line through origin

Question 17

freq with tension - write expression for μ

Answer 17

use fundamental freq formula and then move everything around so μ is o its own

Question 18

freq with tension - how tension measured

Answer 18

using newton balance and weight of pan+contents

Question 19

freq with tension - how you know resonance occurred

Answer 19

-paper rider jumped/fell off

Question 20

freq with tension - state relationship + how graph verifies it

Answer 20

f ∝ √T

straight line through the origin

Question 21

freq with tension -estimate f when tension is 11N using graph (2009 qs)

Answer 21

• find √T so u can find it on the graph

- find f

Question 22

freq with tension - calculate mass per unit length

Answer 22

use fundamental freq formula

Question 23

speed of sound - how length of column of air adjusted

Answer 23

• pipe raised/lowered while immersed in water
• piston moved inside pipe
• moved up + down and held in place using clamp of retort stand
• measure length from top of water to top of tubeusing metre stick

Question 24

speed of sound - how freq of column of air measured

Answer 24

• read frequency from tuning fork of known frequency

- frequency of air in the column = freq of tuning fork

Question 25

speed of sound - how diameter of column of air measured

Answer 25

-internal pipe diameter measured using a vernier calipers

Question 26

speed of sound - how it was known that the air column was vibrating at its first harmonic

Answer 26

first time resonance / loud sound is observed

Question 27

speed of sound - calcuate speed of sound in air

Answer 27

v = fλ
λ = 4(l + 0.3d)

-find vs for diff values of f
and then get average
-unit: m/s

Question 28

speed of sound - how first position of resonance found

Answer 28

• hold vibrating tuning fork over column

- increase length of column until loudest sound is heard from column

Question 29

speed of sound - calculating speed of sound in air

Answer 29

v = 4f(l + 0.3d)

Question 30

speed of sound - why it’s necessary to measure diameter of air column

Answer 30

because wave exists partially above the top of the tube

Question 31

speed of sound - how to find speed of sound in air without measuring diameter

Answer 31

-find distance between first two positions of resonance
l₂ - l₁

-double this distance for wavelength
λ = 2(l₂ - l₁)

-multiply wavelength by frequency
v = fλ

Question 32

speed of sound - equations

Answer 32

c = 4f(l+0.3d)
λ = 4(l+0.3d)
c = fλ

Question 33

speed of sound - finding using graph

Answer 33

c = 4 x slope

Question 34

speed of sound - sources of error

Answer 34

• determining when first harmonic is detected/when first loud sound is emitted, it is difficult to be exact with this position
• percentage error on measuring length, c metre stick is used
• measuring internal diameter of resonance tube

Question 35

freq with length - sources of error

Answer 35

• determining exact length when resonance occurs

- percentage error when using metre stick to measure length

Question 36

freq with tension - sources of error

Answer 36

-determining exact tension when resonance occurs

Question 37

derive an expression for mass per unit length using the slope of the graph and the length

Answer 37

check e-xamit code: whzrbu

Question 38

how to use graph to calculate mass per unit length of string

Answer 38

check e-xamit code: npdeub

Question 39

use data to calculate speed of sound in air

Answer 39

if given the diameter, use formula v = 4f(l + 0.3d)