Johannes Kepler- he did it by observing the ‘Tycho Brahe’. His 3rd law was published 10 years later to his first two laws.
There is no image!?...was there meant to be something attached?
Answer:
19.95 J
Explanation:
The center of mass of the ladder is initially at a height of:

The center of mass of the ladder ends at a height of:
=L/2
So, the work done is equal to the change in potential energy which is:
W = PE = 
now 
therefore
W = [mgL/2]×[1 - sin(theta)]
W = [(7.30)(9.81)(2.50)/2]×[1-sin(51°)]
solving this we get
W = 19.95 J
Answer:
147.456077993 Hz
Explanation:
= Frequency of the sonar = 22 kHz
= Velocity of the whale = 4.95 m/s
v = Speed of sound in water = 1482 m/s
The difference in frequency is given by

The difference in frequency is 147.456077993 Hz