JAMB - Physics (2007 - No. 31)
The fundamental frequency of a plucked wire under a tension of 400N is 250Hz. When the frequency is changed to 500 Hz at constant length, the tension is
1600N
400N
160N
40N
คำอธิบาย
The fundamental frequency is related to tension as
F ∝ √T
∴ T2 = 402 = 1600N
F ∝ √T
| => | F | = K |
| √T |
| ∴ | F1 | = | F2 | => | 250 | = | 500 |
| √T1 | √T2 | √400 | √T2 |
| ∴√T2 = | 500 | √400 = 2 x 20 |
| 250 |
∴ T2 = 402 = 1600N