1. Après la vibration du diapason A, le diapason B vibre. Le diapason B vibre parce que…
A. Le diapason A a la même amplitude que le diapason B.
B. Les deux diapasons utilisent la même boîte de résonance
C. Le diapason B a la même fréquence que le diapason A.
D. Le timbre des sons produits par les deux diapasons est identique.
Solution
After vibrated, the tuning fork A vibrates the surrounding air, so the air also vibrates with the same fréquence. Furthermore, the air vibrates the tuning fork B. The tuning fork B is also vibrating with natural frequency, but the amplitude of the vibration is minimal, and the vibration is not visible. Since the natural frequency of the tuning fork B is equal to the frequency of the air vibration,
and the frequency of the tuning fork A, then the air molecule amplifies the amplitude of the tuning fork B. The tuning fork B appears to vibrate because its amplitude of vibration is visible.
La bonne réponse est C.
2. La résonance tube produces a loud sound at the first time when the length of the air column is 17 cm and a loud sound at the second time when the length of the air column is 51 cm. The tuning fork frequency used is 500 Hz. Determine the speed of the air in the tube.
A. 138 m/s
B. 230 m/s
C. 340 m/s
D. 461 m/s
Solution:
The shape of the resonance tube is one end is open, and the other end is closed, so the distance between the node and anti-node = the minimum length of tube = ¼ λ = λ / 4.
The equation of the length of the tube :
The distance between the node and an anti-node of the tube of resonance with one end is open, and another end is closed, fulfilled when n is an odd number
La bonne réponse est C.
3. The first resonance in the tube of resonance occurs when the length of the air column is 20 cm. The second resonance and the third resonance happen when the length of the air column is…
A. 40 cm and 60 cm
B. 30 cm and 40 cm
C. 60 cm and 100 cm
D. 100 cm and 200 cm
Connu :
The length of the air column if n1 = 1 (L1) = 0.2 m
Recherché : The length of the air column if n2 = 3 et n3 = 5
Solution:
The equation of the length of the tube (equation of the length of air column) :
Use this equation to calculate the Longueur des ondes using the above data :
The length of the air column when n2 = 3 :
La bonne réponse est C.
