Everyday high and low tides on earth will happen daily about . * Every 12 hours
Every 4 hours
Every 6 hours
Every 8 hours

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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not too sure thinking all accelerations are pointed down

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.