Practice question

**Mechanical waves** require medium and can be transverse or longitudinal. Sound in air is longitudinal since fluids support only compressional motion, while string waves are transverse. Progressive waves transfer energy without net mass transport, distinguishing from standing waves. Speed: v = √((B/rho)) . 1500 = √((2.25 × 10⁹/rho)) ⇒ 1500² = (2.25 × 10⁹/rho) . rho = (2.25 × 10⁹/1500²) = (2.25 × 10⁹/2.25 × 10⁶) = 1000 kg/m³ . Using v = fλ and standing-wave condition fₙ = n v/(2L) or v/(4L) as applicable, calculation yields 1000 kg/m³, illustrating frequency-length-speed interdependence and quantization by boundaries.