waec model questions vol1 2021 physics
Objective • Question 7
Question 7
WAEC_MODEL_QUESTIONS_VOL1
•
2021
A string 1.20 m long is fixed at both ends and vibrates in its third harmonic with a frequency of 180 Hz. The linear mass density of the string is 0.025 kg m⁻¹. (a) Calculate the speed of the transverse wave on the string and the tension in the string. (b) If the tension is increased by 20 % while the string length remains unchanged, what is the new frequency of the third harmonic.
Answer Options
Correct Answer
A.
Wave speed = 144 m/s; tension = 5.18×10² N; new frequency ≈ 197 Hz
B.
Wave speed = 130 m\/s; tension = 4.70×10² N; new frequency ≈ 185 Hz
C.
Wave speed = 120 m\/s; tension = 3.90×10² N; new frequency ≈ 170 Hz
D.
Wave speed = 158 m\/s; tension = 5.80×10² N; new frequency ≈ 210 Hz
Correct Answer
A
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