Answer:
Electromagnetic waves do not require a medium in order to transport their energy. Mechanical waves are waves that require a medium in order to transport their energy from one location to another. ... Sound is a mechanical wave and cannot travel through a vacuum.
Answer:25.61 m/s
Explanation:
Given
truck is moving eastbound with a velocity of 16 m/s
Velocity of truck 
SUV is moving south with a velocity of 20 m/s
Velocity of SUV in vector form 
Velocity of truck relative to the SUV


Magnitude of relative velocity is

Farmula 2gh=vf²-vi²
2×0.42×9.81=0²-vi²
8.2404=vi²
Vi=✓8.2404
Vi=2.87m/sec