Question

(a) What is resonance and the conditions for resonance? Give examples. (b) What is the Doppler effect, and how is it produced? Cite two examples. (c) Why does a police siren sound different when it’s approaching you and when it’s passed you? Explain what is happening as thoroughly as possible. (d) What are the similarities and differences between Coulomb's law and Newton's law of gravitation?

Answer 1

a) In physics, there are a lot of systems that have nature to oscillates with larger amplitude on such frequency and that condition is called resonance. The highest frequency is called the resonant frequency.

Condition: 1) The system must have a natural frequency and a driving force whose frequency the same as the natural frequency.

2)The effect of friction or any dissipation must be the least.

Example: 1) Musical instruments have special arrangements for sound resonance.

              2) Laser light is produced by optical resonance.

b) Doppler effect: The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the source.

This effect is occurred mainly due to the relative motion between source and an observer.

Example: 1) A common example of Doppler shifts the change of a pitch heard when a vehicle sounding a horn approaches and recedes from an observer.

2) Doppler effect is also used to diagnose heart problems and meteorologists to track stroms.

c) Police siren sounds different in a different situation due to the Doppler effect. When it approaches someone it sounds louder just due to relative motion. When it passes someone the intensity of sound will be decreased.

d) Coulomb's law is based on the force acting on two charge particle and Newton's law is based on Gravitational force. The main similarity is both the force is inversely proportional to the square of the distance.