Physics (AS & A Level) · Oct / Nov 2023 · Paper 11 · Question 22

A toy drone emits a sound of constant frequency 800 Hz. The speed of the sound in the air is 330 m s⁻¹. The drone moves along a straight path directly towards an observer and then continues in a straight line directly away from the observer. The speed of the drone is constant. [diagram: toy drone moving along a dashed straight path towards and past an observer] What is the velocity of the drone when the frequency of the sound heard by the observer is 850 Hz?

1. Amagnitude of velocity 19 m s⁻¹, direction away from the observer
2. Bmagnitude of velocity 21 m s⁻¹, direction away from the observer
3. Cmagnitude of velocity 19 m s⁻¹, direction towards the observer
4. Dmagnitude of velocity 21 m s⁻¹, direction towards the observer

As printed in the paper