# The earth surface or a point at infinity from the earth can be chosen as zero reference level of? (a) Electric P.E. (b) Kinetic Energy (c) Gravitational P.E. (d) All of the above. I am unable to figure the given statement for option (b).

Jul 10, 2017

The quick answer to this is (d) All of the above for the earth surface.

#### Explanation:

The electrical potential energy is self defined as ground, or zero volts here on earth.
https://en.wikipedia.org/wiki/Ground_%28electricity%29

Kinetic energy is chosen as zero on the earth's surface for most items that are falling (moving towards the core) on earth, since we consider that nothing can fall into it. Meteorites may argue the point.

This analysis refers to objects large enough to be not considered by their quantum state, which is a whole different topic, and objects that possess no momentum in any direction.
If you want to prevent damage to an object due to falling, place it down low. Nothing has ever fallen off the floor.

Gravitational potential energy also takes earth ground as its zero point, because any other reference would not be (approximately) the same everywhere on earth.
http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/gravpe.html

Looking at the infinite distance away:
The electrical would be too infinitesimal to be readable.
The KE would not occur because there would be other attractions out there that would overpower any earth effect.
The gravitational PE would be eliminated by the distance.