To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as

Here,
=frequency received by detector
=frequency of wave emitted by source
=velocity of detector
=velocity of source
v=velocity of sound wave
Replacing we have that,


Therefore the frequencty that will hear the passengers is 422Hz
Answer:
The tension in the string is 16.24 N
Explanation:
Given;
mass of the sphere, m = 1.55 kg
initial velocity of the sphere, u = 2.81 m/s
final velocity of the sphere, v = 4.60 m/s
duration of change in the velocity, Δt = 2.64 s
The tension of the string is calculated as follows;

T = 1.55(0.678 + 9.8)
T = 1.55(10.478)
T = 16.24 N
Therefore, the tension in the string is 16.24 N
Steel tray because steel is an iron-carbon alloy