A7LAM CSCA ACADEMYCSCA Academy / Physics / Mechanics
CSCA Physics · Lesson 6 of 16Oscillations and waves
Oscillations et ondes · الاهتزازات والموجات
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A mass on a spring and a pendulum repeat their motion: simple harmonic motion. When an oscillation travels through a medium, it becomes a wave.
Key ideas
- Wave speed v = f·λ (frequency in Hz, wavelength in m).
- Period T = 1/f.
- Pendulum: T = 2π√(L/g); spring: T = 2π√(m/k).
- Transverse waves vibrate across the direction of travel; sound is longitudinal.
Formulas to know
- v = fλ
- T = 1/f
- T = 2π√(L/g)
Worked example
A sound wave has frequency 170 Hz in air (v = 340 m/s). Find its wavelength.
- λ = v / f.
- λ = 340 / 170.
Answer: λ = 2 m
Practice questions
1. A wave has period 0.02 s. Its frequency?
0.02 Hz · 2 Hz · 50 Hz ✓ · 200 Hz
f = 1/T = 1/0.02 = 50 Hz.
2. A pendulum is made 4 times longer. Its period:
doubles ✓ · is ×4 · halves · stays the same
T ∝ √L, √4 = 2.
3. A wave travels 30 m in 2 s with λ = 3 m. Frequency?
5 Hz ✓ · 10 Hz · 15 Hz · 45 Hz
v = 15 m/s, f = 15/3 = 5 Hz.