# Tidal Forces

by roz77
Tags: forces, tidal
 HW Helper PF Gold P: 1,961 If you know calculus, you can find the relative acceleration by using the formula $$a(r + dr) - a(r) = \frac{d}{dr}a(r)dr$$ Where a(r) is the acceleration due to the earth at distance r, and dr is the distance between the two balls (1 m in this case). This is a reasonable thing to do because 1m is very small compared to 2000km, and the rate at which a(r) changes over such small distances is approximately constant (i.e. is of first order in r) Once you know the relative acceleration, you have to find out the time needed for this acceleration to produce a difference in distance of 0.01m. (Hint: do you recognize this formula: $$s = (1/2)at^2$$?).