LSS Chapter 16 Sound

LSS Chapter 16 Sound

Mr. Fu

Multiple Choice

In an experiment, some grains of sand were placed on a speaker. The volume of the music coming from the speaker was increased gradually. The grains of sand on the speaker jumped about more vigorously. This means that...

• the pitch of the sound had increased

• the loudness of the sound had increased

• the quality of the sound had decreased

• the speed of sound had decreased

Multiple Choice

How is sound carried away from its source?

• By vibrations transferred from one molecule to the next

• By molecules moving away from the source at 300 m/s

• By waves moving out in the spaces between molecules

• By ropes shaking up and down to form rippling waves

Multiple Choice

Tim uses a hammer to strike one end of a long metal pipe. Dennis stands at the other end of the pipe and hears two sounds. Dennis hears the first sound almost immediately after Tim strikes the pipe. Dennis then hears another sound 1 second after Tim’s first strike.

Why does Dennis hear two sounds instead of only one? Explain your answer.

• Tim actually hit the pipe twice, although the question uses the word "strike"

• The metal pipe vibrates so much that it creates multiple waves of sound, causing Dennis to hear multiple sounds

• The sound is so large that it causes damage to Dennis's ears, causing him to hear multiple sounds

• The sound of the strike is travelling through both the metal pipe and the air at different speeds, resulting in two sounds being heard at different times

Multiple Choice

Tim uses a hammer to strike one end of a long metal pipe. Dennis stands at the other end of the pipe and hears two sounds. Dennis hears the first sound almost immediately after Tim strikes the pipe. Dennis then hears another sound 1 second after Tim’s first strike.

Given that the speed of sound in air is 330 m/s, estimate the length of the pipe.

• 329 m

• 330 m

• 331 m

Multiple Choice

Which parts of the ear vibrate when sound is heard?

• External ear and ear canal

• Ear bones and eardrum

• Ear bones and eardrum

• Ear bones and ear canal

Open Ended

Studies have shown that loud noises have negative effects on our hearing. Moira enjoys listening to loud music using earphones. She says that her hearing will never be affected as the loudness of the music is only 90 dB (decibels). (Hint: The threshold of pain is 125 dB.)

Do you agree with Moira’s explanation? Explain your answer.

Open Ended

A musician plucks a string of a violin. Explain why he cannot change the pitch of the musical note by plucking the string harder or more gently.

Multiple Choice

Which event is one where sound is not useful?

• At a conference, for giving speeches to the participants

• At an orchestral concert in a large hall to the audience

• At a coffee shop near roadworks with a pneumatic drill in use

• At home with the family watching the World Cup on TV

Multiple Choice

Which of the following is not a use of sound?

• Sonar

• Fire alarms

• Growling of guard dogs

• Rumbling of thunder