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## Homework Statement

when g = constant ,

**time**= v / g

**if g varies how do I get t ?**

One electron is at rest at r0, 3600 km from surface of Earth (r), 10.000 km from center.

g(r) = 9.8 m/s^2 , g(r0) = 4, Δ PE = 2.25 x 10^7

1) If it fell in a vacuum, after

*how many seconds*would touchdown?

## Homework Equations

(a) v = sqrt( 2x PE), (b) g= PE/ h

## The Attempt at a Solution

from (a) => v = sqrt ((2 x2.25) 4.5 x 10^7) = 6,708 m/s

from (b) => average g = 2.25 x 10^7 / 3,600,000 = 6.25 m/s^2, t= 6708/6.25= 1273 s

## Homework Statement

2)

*ceteris paribus*, if we change gravity with elecrostatic attraction, then drop of Potential becomes 0.0009305 eV,and final v seems to change from 6,7 to 18,1 km/ s.WHY?

## Homework Equations

## The Attempt at a Solution

no idea