Which would describe a situation in which the doppler effect is occurring? sheila notices an increase in volume as an object approaches her. brad hears an object increase in loudness as it is vibrated at its natural frequency. judy notices an increase in intensity as an object is vibrated at its natural frequency. damian hears a change in pitch as an object moves past him.?

The demonstration of the Doppler effect is when Damian hears a change in pitch as an object moves past him.
The Doppler effect, explained by Christian Doppler, describes the change in frequency or wavelength of an emitted wave due to motion of either the source or the observer in relation to one another. 
Simply explained, the crests of a wave become clumped together if the source moves towards the observer and they move further apart if the source moves away from the observer.

This is the answer: body 1 + engine 2

The object's initial distance above the groundthe object's initial velocity