Buzz
Solve Exercise C1 on page 28 SGK Physics 7
Exercise:
Problem Statement:
List some sources of sound.
Solution:
Some sources of sound: trumpet, flute, drum, electric fan, car engine...
Solution for problem C3 on page 28 of Physics 7 textbook
Problem Statement:
Observe the rubber band and listen carefully, then describe what you see and hear.
Solution:
The rubber band vibrates and produces sound.
Solution for problem C4 on page 29 of Physics 7 textbook
Problem Statement:
Which object emits sound?
Does the object vibrate? How can you determine that?
Solution:
- The glass cup emits sound.
- The glass cup vibrates.
- Detect the vibration of the glass cup by: Hanging a pendulum close to the glass cup. When tapping the spoon against the glass cup, the pendulum swings, indicating that the glass cup is vibrating.
Solution for problem C5 on page 29 of Physics 7 textbook
Problem Statement:
Does the tuning fork vibrate? Find a way to check if the tuning fork vibrates when producing sound.
Conclusion
When emitting sound, all objects .....
Solution:
- The tuning fork vibrates:
- The vibration of the tuning fork can be checked using one of the following methods:
+ Place a pendulum close to one prong of the tuning fork when it emits sound.
+ Use a piece of paper to touch one prong of the tuning fork; if the paper vibrates, it indicates that the tuning fork is vibrating.
+ Use your hand to stretch a piece of rubber band and touch one prong of the tuning fork to the stretched band when it emits sound.
- Conclusion: When emitting sound, all objects vibrate.
Solution for problem C6 on page 29 of Physics 7 textbook
Problem Statement:
Can you make some objects like paper, banana leaves,... emit sound?
Solution:
Some objects like paper, banana leaves... can emit sound by one of the following methods:
- Tear the paper, banana leaves...
- You can roll the paper or banana leaves into the shape of a horn and blow on it, the horn will produce sound.
Solution for problem C7 on page 29 of Physics 7 textbook
Problem Statement:
Investigate which part vibrates to produce sound in two musical instruments you know.
Solution:
- Guitar: the vibrating part producing sound is the guitar strings.
- Drum: the vibrating part producing sound is the drumhead.
Solution for problem C8 on page 29 of Physics 7 textbook
Problem Statement:
If you blow into the mouth of a small bottle, the air column inside the bottle will vibrate and produce sound. Find a way to check if the air column vibrates in this case.
Solution:
The vibration of the air column inside the bottle can be checked by:
+ Stick a thin paper strip onto the mouth of the bottle, when blowing into the bottle, it produces sound and the paper strip vibrates.
+ Put a few tiny paper scraps into the bottle, when blowing into the bottle, it produces sound and the paper scraps fly up and down. This proves that the air inside the bottle has vibrated, causing the paper scraps to fly.
Solution for problem C9 on page 29 of Physics 7 textbook
Problem Statement:
Make a musical instrument (test tube xylophone) following the instructions below:
- Pour water into seven identical test tubes to different water levels (figure 10.4).
- Use a spoon to gently tap each test tube in turn to hear different bass and treble sounds.
a) Which part vibrates to produce sound?
b) Which tube produces the deepest bass sound, and which tube produces the highest treble sound?
- Blowing forcefully into the mouths of the test tubes will also produce different bass and treble sounds (figure 10.5).
c) What vibrates to produce sound?
d) Which tube produces the deepest bass sound, and which tube produces the highest treble sound?
Solution:
a) The test tube and the water inside the test tube vibrate to produce sound.
b) The tube with the most water produces the deepest bass sound, and the tube with the least water produces the highest treble sound.
c) The column of air inside the tube vibrates to produce sound.
d) The tube with the longest air column produces the deepest bass sound. The tube with the shortest air column produces the highest treble sound.
The convex mirror is a vital lesson in Chapter I of Optics. Check out hints for solving exercises on pages 20 and 21 of Physics 7 to grasp the concept better.
In Chapter I of Optics in Physics 7, students will engage in Practical Work: Observing and sketching an image formed by a flat mirror alongside solving exercises on page 18.
