Answer:
Christian Doppler
Explanation:
The Scientist with the most significant contribution to the discovery of planets around other stars is Christian Doppler and his work that made this discovery possible is the Principle of DOPPLER EFFECT
<em>Christian Doppler was an Austrian scientist and physicist whose principle Doppler effect explained how observed frequency of light and sound waves are affected by a relative motion of both the source and detector </em>
Freefall is when you don't have any control over your body, you have gravity pulling you down to the center of the earth, while weightlessness you have the ability to float, go down, move side to side. In weightlessness you have zero gravity, but while your freefalling you are in gravity.
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It does not affect the objects potential energy.
Swimming, because during swimming we use more muscles than when we sprint, stretch, etc..
Answer: Delta U = 30 - 80; -50 jules
Explanation:
The system is losing 80 J, but it is also gaining 30 J because the surroundings are doing work on it. So the net change in energy is -50 J