What Angular Speed Must Earth Rotate for Equatorial Weight to Drop by 25%?

[9giddjl]

Angular Speed of Earth when...

Homework Statement

Determine the angular speed with which the Earth would have to rotate on its axis so that a person on the equator would weigh 75% of their present weight (Radius of the Earth is 6400 km)

Homework Equations

wf=2pi/T
wt= mg
v=wr

The Attempt at a Solution

First I did wt=0.75 x m x 9.8, the problem is i can't find any equation that could incorporate weight and angular speed. Can somebody please give me some hints? Any help would be appreciated:) Thankyou very much

 

[mgb_phys]

Centrifugal force = m r w^2 where w is the angular speed in radians/sec.