Answer:
754.6 m
Explanation:
The GPE (Gravitational potential energy) of an object with respect to the ground is given by

where
m is the mass of the object
g = 9.8 m/s^2 is the acceleration due to gravity
h is the heigth above the ground
Here we have
m = 12,400.05 kg is the mass
GPE = 91,700,000.00J is the GPE
Solving the formula for h, we find the heigth:

The change in pitch of a train's horn as it passes while you are standing still can be explained by the Doppler effect. The correct option among all the options given in the question is option "A". When the sound source from the horn of the train comes closer, the sound seems to come closer each time a sound wave gets emitted. So it comes closer to us in a bunched form. The reverse happens when the train has just passed with each emitted sound going further and further away. The frequency of the sound seems to get lower as the train moves further away.
(1) Speed is the ratio of the total distance covered by the object and the total time it takes for him to finish it.
Speed = distance / time
In this item, we are given that the distance is 20 kilometers and that the time it takes for the trip is 2 hours. Substituting the known values,
Speed = 20 kilometers / 2 hours
speed = 20 km/h
(2) Velocity on the other hand takes into account the displacement of the object from his original position. It is assumed that Jeremie was basically back to his original position after two hours. Hence, the velocity is equal to zero.