Mahi Tuatahi ^🔗

P3.3 Worksheet #4 Q2a, b

Doppler Skill 2: Finding $v_{s}$ ^🔗

This is relatively straightforward when $f$ and $f’$ are known. It becomes more challenging when you do not have both of these variables – we will address this later.

$$ \begin{aligned} & f’ = f\frac{v_{w}}{v_{w} \pm v_{s}} \end{aligned} $$

1. Identify when you are in a $+$ or a $-$ situtation,
2. Substitute your knowns,
3. Simplify and re-arrange to solve.

Pātai: The Airport ^🔗

Cameron is watching a plane by the airport. Its engines emit sound at $2000Hz$; the speed of sound in air is $330ms^{-1}$.

1. He hears a frequency of $2500Hz$ as it approaches him. What is the velocity of the plane?
2. He hears a frequency of $1250Hz$ as it has passed him. What is the velocity of the plane?

Pātai: Doppler Ultrasound ^🔗

• A Doppler ultrasound is used to measure the flow of blood in blood vessels. This can be used to help find blood clots or constricted vessels. The ultrasound operates at $4MHz$ and the speed of sound in flesh/blood is around $1500ms^{-1}$.
• If the return frequency is $4,005,073.09Hz$, calculate the velocity of the blood towards the device.

Fast Finishers: P3.3 Worksheet #4 Q1a, b