- #1
d_jnaneswar
- 37
- 0
hi guys,
I have a doubt, and searched this forum, but couldn't find an answer.
Law of conservation of energy states that energy can neither be created nor destroyed. In other words, energy can convert from one form to another, but as a whole, in a system, its quantity does not change.
Am I right?
How can we apply this to the Universe? How can we say that it is certainly true for the entire universe?
Another question.
In the archives, I came across a thread that had a rough discussion on planets and energy spent to keep them in orbit.
The question is, is gravitational force based on energy? Doesnt Earth need a constant source of energy to keep a massive object like moon in orbit?
The other thread said that the work done by Earth on moon is zero since..
a) work done on an object moving in a circle is zero.
b) force on moon is perpendicular to the direction of movement of the moon and so, the energy spent is zero in that direction (assuming that moon travels in a perfect circle).
If this is so, then Earth does not spend energy in keeping the moon there. yet, the moon stays there fighting the centrifugal pull. The answer is gravitational force. But if gravitational force doesn't equal the energy of the centrifugal pull or any other pulls in the opposite direction, how can it stay in orbit?
Also, if Earth doesn't spend energy on it to keep it in orbit, doesn't that mean that gravitational pull is not involved with energy on an object? Then what about potential energy?
You see my doubt? I am a bit confused here. Please explain the relationship between gravity and energy.
Gravity is G*m1*m2/d*d right? (where G is gravitational constant). Its been almost 15 years since I read this formula, so please correct. And energy/work is Force * distance. which means work = mass * acceleration * distance. right?
DJ
I have a doubt, and searched this forum, but couldn't find an answer.
Law of conservation of energy states that energy can neither be created nor destroyed. In other words, energy can convert from one form to another, but as a whole, in a system, its quantity does not change.
Am I right?
How can we apply this to the Universe? How can we say that it is certainly true for the entire universe?
Another question.
In the archives, I came across a thread that had a rough discussion on planets and energy spent to keep them in orbit.
The question is, is gravitational force based on energy? Doesnt Earth need a constant source of energy to keep a massive object like moon in orbit?
The other thread said that the work done by Earth on moon is zero since..
a) work done on an object moving in a circle is zero.
b) force on moon is perpendicular to the direction of movement of the moon and so, the energy spent is zero in that direction (assuming that moon travels in a perfect circle).
If this is so, then Earth does not spend energy in keeping the moon there. yet, the moon stays there fighting the centrifugal pull. The answer is gravitational force. But if gravitational force doesn't equal the energy of the centrifugal pull or any other pulls in the opposite direction, how can it stay in orbit?
Also, if Earth doesn't spend energy on it to keep it in orbit, doesn't that mean that gravitational pull is not involved with energy on an object? Then what about potential energy?
You see my doubt? I am a bit confused here. Please explain the relationship between gravity and energy.
Gravity is G*m1*m2/d*d right? (where G is gravitational constant). Its been almost 15 years since I read this formula, so please correct. And energy/work is Force * distance. which means work = mass * acceleration * distance. right?
DJ