Doppler Effect for Sound

A tutorial sheet on the Doppler effect for sound waves is given below.

1. State a definition of the Doppler effect for sound waves.
2. A train moves to the east at a speed v. The speed of sound in air is v_s. The train emits sound waves. Find the speed of the sound waves (a) in front of the train, (b) behind the train
3. A fire truck has a siren of frequency f. The truck moves at a constant velocity v relative to the ground. The speed of sound in air is v_s. What is the frequency of the sound waves heard by a stationary observer as the truck approaches them?
4. In question 2 does the frequency of the sound heard by the observer increase, stay the same or decrease as the fire truck approaches?
5. A train has a whistle of frequency f that emits sound waves that travel through air at a speed v_s. The train moves at a speed u to the east. A second train moves to the east at a speed v, where u is less than v. Is the frequency of the sound waves heard on the second train f(v - u)/v_s?

6. A train has a whistle of frequency f that emits sound waves which travel through air at a speed v_s. The train moves at a speed u towards a tunnel in a vertical mountain. Is the frequency of the reflected sound waves heard on the train 2fu/v_s?

7. A physics student drops a vibrating 440 Hz tuning fork down an elevator shaft in a tall building. When the student hears a frequency of 400 Hz, how far has the tuning fork fallen? Take the speed of sound in air as 340 m s^-1. (Tippler, Physics, second edition, p 483)

IB HL Physics Poorly Answered Questions 3

A third tutorial sheet of questions on poorly answered HL concepts is given below.

1. A 6 Ω resistor is connected in series with a cell of emf 12 V of zero internal resistance, an ideal ammeter and an ideal voltmeter. Find the reading on each meter.
2. State the definition of emf.
3. An electron is in the fourth excited state of the hydrogen atom. How many different spectral lines could appear in the emission spectrum of this atom?
4. The strong nuclear interaction between two protons (a) can be equal to zero (b) is repulsive for distances less than 3 fm, (c) is attractive for distances less than 3 fm, (d) is always greater than the Coulomb interaction between the protons
5. A particular radioactive substance undergoes β^- decay. Does the daughter nuclide always have the same energy?
6. Two positive point charges are at a fixed distance apart. When the electric field due to the charges is zero the electric potential is (A) zero, (B) a maximum value, (C) a minimum value, (D) not defined
7. In quantum tunnelling (A) the particle tunnels under the obstacle and fully appears on the other side (B) the particle is described by a wave function that exponentially decays through the barrier and is detected with less energy on the other side (C) the particle is described by a wave function that exponentially decays through the barrier and is detected with the same energy on the other side (D) the particle passes through the barrier instantaneously (see Nature July 22, 2020)