QUESTION 9 The intensity of a sound is amplified from 20 µW/m2 to 2 mW/m2. Calculate the amplification in dB. QUESTION 10 In a hydraulic car lift, the input piston has a radius of 2 cm and a negligible weight. The output plunger has a radius of 0.4 m. The combined mass of the car and the plunger is 1.2 tonne. The hydraulic lift uses hydraulic fluid. What input force (in N) is needed to support the car and the output plunger when the bottom surfaces are at the same level? QUESTION 11 The length of a steel bridge increases by 90 mm when the temperature changes from -9 °C to + 21 °C. Find the original length of the bridge (in m). Note the coefficient of linear expansion for steel is 12 x 106 °c-1.
Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
Quality Of Sound
A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
Categories of Sound Wave
People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
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