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Solution for Exercise C1 Page 28 Physics 7 Textbook
Exercise:
Let's all maintain silence and listen attentively. Identify the sounds you hear and trace their origins.
Solution:
Audible sounds: whirring of a fan, rumble of a motorcycle passing by, teacher's voice lecturing,...
Solution for problem C2 page 28 Physics textbook Grade 7
Problem:
List some sources of sound.
Solution:
Some sources of sound: trumpet, flute, drum, electric fan, car engine...
Solution for exercise C3 page 28 Physics textbook Grade 7
Problem:
Observe the rubber band and listen, then describe what you see and hear.
Solution:
The rubber band vibrates and produces sound.
Solution for problem C4 page 29 Physics textbook Grade 7
Problem:
Which object emits sound?
Does the object vibrate? How can you determine that?
Solution:
- The glass cup emits sound.
- The glass cup vibrates.
- Detecting the vibration of the glass cup by: Hanging a pendulum close to the glass cup. When tapping the glass cup with a spoon, the pendulum swings, demonstrating that the glass cup vibrates.
Solution for problem C5 page 29 Physics textbook Grade 7
Problem:
Does sound transmit vibrations? Find a way to check whether the soundboard vibrates when producing sound.
Conclusion
When emitting sound, all objects ....
Solution:
- The soundboard vibrates:
- The vibration of the soundboard can be tested by one of the following methods:
+ Place a pendulum close to a branch of the soundboard when it emits sound.
+ Use a piece of paper to touch a branch of the soundboard, noticing the paper vibrating, indicating the soundboard is vibrating.
+ Stretch a rubber band and touch a branch of the soundboard to the stretched band when the soundboard produces sound.
- Conclusion: When emitting sound, all objects vibrate.
Solution for problem C6 page 29 Physics textbook Grade 7
Problem:
Can you make some objects like paper, banana leaf... produce sound?
Solution:
Some objects like paper, banana leaf... can produce sound by one of the following methods:
- Tear the paper, banana leaf...
- Roll the paper or banana leaf into the shape of a trumpet and blow, it will produce sound.
Solution for exercise C7 page 29 Physics textbook Grade 7
Problem:
Investigate which part vibrates to produce sound in two musical instruments you know?
Solution:
- Guitar: the vibrating part producing sound is the guitar string.
- Drum: the vibrating part producing sound is the drumhead.
Solution for problem C8 page 29 Physics textbook Grade 7
Problem:
If you blow into the mouth of a small bottle, the column of air inside the bottle will vibrate and produce sound. Find a way to check if the air column vibrates at that time.
Solution:
The vibration of the air column inside the bottle can be tested by:
+ Attach a thin piece of paper to the mouth of the bottle, when blowing into the bottle it emits sound and the paper can be seen vibrating.
+ Put some tiny pieces of paper into the bottle, when blowing into the bottle it emits sound and the paper can be seen flying up and down. It shows that the air inside the bottle has vibrated causing the paper to fly.
Solution for problem C9 page 29 Physics textbook Grade 7
Problem:
Make a musical instrument (test tube xylophone) according to the instructions below:
- Pour water into seven identical test tubes to different water levels (figure 10.4).
- Tap lightly on each test tube one by one to hear different low and high sounds.
a) Which part vibrates to produce sound?
b) Which tube produces the lowest sound, and which tube produces the highest sound?
- Blowing forcefully into the mouths of the test tubes will also produce different low and high sounds (figure 10.5).
c) What vibrates to produce sound?
d) Which tube produces the lowest sound, and which tube produces the highest sound?
Solution:
a) The test tubes and the water in the test tubes vibrate to produce sound.
b) The tube with the most water produces the lowest sound, and the tube with the least water produces the highest sound.
c) The column of air inside the tube vibrates to produce sound.
d) The tube with the longest air column produces the lowest sound. The tube with the shortest air column produces the highest sound.
The convex mirror is a crucial lesson in Chapter I Optics. Let's explore the hints for Exercise Solutions on pages 20, 21 Physics Grade 7 to understand the concept better.
In Chapter I Optics of Physics Grade 7, students will learn the Practice: Observing and drawing images of an object formed by a flat mirror along with Exercise Solutions on page 18 Physics Grade 7.
