escape velocity

There is an attractive force between the object and earth. The initial kinetic energy of the object has been all changed into potential energy at infinity.


2015-07-28 19:21:58 補充：
The situation is just the same as throwing an object (e.g. a ball) vertically upward from earth surface. After the object leaves the thrower's hand, its velocity is continuously slowed down by the gravitational attractive force of the earth.

2015-07-28 19:25:22 補充：
(cont'd)...
As the object goes up, its kinetic energy changes into (gravitational) potential energy. The velocity of the object becomes zero when its initial kinetic energy has all been changed into potential energy. Thus, the higher the initial velocity, the higher in height the object can reach.

2015-07-28 19:27:27 補充：
(cont'd)...
If the initial velocity of the object is high enough, it would reach infinity withou being stopped by gravity.

2015-07-28 19:30:02 補充：
(cont'd)...
An object can only move at uniform speed by inertia if there is no external net force acting on it. But in the situation you described, there is an external force, gravity, that acts on the object during its motion.

溫馨提示(增加知識):
其實無可能0
A: acceleration field
del(A)=4(3.1415926535897932384626433...)GToo+lambda
When Too(which is the energy density)--->0,
dA=lambda( dx,dy,dz )
A=lambda ( r ) ------>Acceleration field is proportional to distance
lambda=constant------->暗能量(Dark energy)