#Non impulsive force free

The work done by gravity is still just going

This initial point to the final point, and Gravity only depends on the initial and final In other words, the work doneīy the gravitational force doesn't depend on the specifics Joules, just like it was when the mass was That means that the total workĭone on the mass from gravity is still 294 Since the gravitational force is pointing in the opposite The work done by gravityįor the first downwards trip was 294 joules.

If the mass moves downwardsīy an amount of 6 meters, the work done by gravity For instance, the gravitationalįorce on a 5 kilogram mass is 49 newtons. If the work done by aįorce follows this rule, then we call it aĬonservative force. In other words, the work done byĪ conservative force on a mass does not depend on the That force on an object only depends on the initial andįinal positions of the object. What's a conservative force? Conservative forces

#Non impulsive force free

Most astronomers choose to say that if an object has enough KE to get free from a big gravitational object, then it has positive ME, but if it is trapped by the big object, then the negative PE is greater in magnitude than the positive KE, so the ME is negative. It has some KE, since it is moving in its orbit, but not enough to get free from the sun. Here is another very real-life example: the earth has negative mechanical energy, if you ask almost any astronomer! The reason is that the earth is 'down in a hole' relative to the sun's gravitational pull. So to give you an example, if we are holding an object at y = 0 (say, ground level), and our friend is down in a hole (say, y = -10m), and we drop the object and he catches it and holds it at rest, then it has KE = 0 and PE = mgy < 0, so ME < 0. We just make the choice that we think will make calculations easiest. It can be the height where the object starts, where it finishes, the height of the ground level, or any other height. But the y = 0 height can be whatever you want. For example, we usually say that gravitational potential energy PEg = mgy, where y is the height of the object. In fact, PE is very often negative, but an extremely important fact about PE is that it is always up to YOU to decide what position is the PE = 0 position. KE is never negative, and it can only be 0 if the object is not moving.