What is the potential energy of a body at the sea level?
Answers
Answer:
A good example of this is kinetic energy. You tend to think of”stationary” as being no kinetic energy. If you were on a train travelling at about 100 mph and you threw a ball to you friend opposite you, your friend would almost certainly would estimate the KE of the ball based on it moving at about 5 mph. They would choose the train as the stationary object and say the ball is moving at 5mph and calculate the KE from that. That is OK.
If you were in an upstairs room and you threw a ball upwards at the highest point would you calculate the PE based on the height above the floor in the building, the height above the ground outside or the height above sea-level (the building could be in mexico city (which is pretty high!). Any of these are OK.
Some practical help with text book/ examination questions about gravitational PE. Always check carefully and before you make a start - decide whether the question is set on earth - balls/planes /cars on hills etc or are they about planets /stars spaceships.
DEpending on which type of question you decide it is there are two seemingly different methods.
For questions set about earth bound situations you can use PE= mgh and use g=9.8N/kg (or whatever value the question gives) and mereasure height from any point you like provided you are then consistent.
For space type questions there is a convention that we set the zero point as being far away in space and the PE is minus (-) the energy required to move an object from its current position off to a very distant point (infinity). For these questions you use PE=-GMm/r where r is the distance FROM THE CENTRE OF THE PLANET ( even though we are talking about moving the object off ino space). Finally you can’t use g=9.81 or any other fixed value because the movement of the object is on a scale such that g (graviational field strength does change).
After writing all this I was about to say use PE = -GMm/r when I noticed that in the question you havent give the mass of the body you want to know about so the short answer is that isd depends on the mass of the body ( and on the mass of the earth of course)