 #1
RemotePhysics
Gold Member
 22
 3
Homework Statement:

The diameter of earth is 12,700 km. Calculate :
a> The angular velocity at which earth is spinning
b> The speed at which someone standing on the equator is rotating relative to the pole
Weighting scales do not measure your mass, just the reaction force R that the scales push back on you.
c> Write an equation for the centripital force F in terms of R and weight W for someone rotating
on earth
d> Hence show that the scales would give a reading of approximately 99.7% of the person's
actual mass (ignoring any inacuracy due to the scales)
e> How fast in m/s, would the earth have to be spinning, for someone at the equator to "fly off"?
How long would a day be in this situation?
Relevant Equations:

w=v/r
F = W  R ???
My solutions (attempts) :
a> w=v/r  r=6.35x10^6m  therefore V=7.04x10^5 m/s
b> speed of rotation is faster at the equator than the pole as w=v/r. As w remains constant, as r increases towards the pole V has to decrease.
c> F = W  R
d> Stuck here. I presume that I have to use the equation from part C and gravity must be a factor but I am unsure of how to work this one out!
e> No idea how to work this out? Am I meant to google an equation for speed of rotation and the length of a day!? What would you do?
a> w=v/r  r=6.35x10^6m  therefore V=7.04x10^5 m/s
b> speed of rotation is faster at the equator than the pole as w=v/r. As w remains constant, as r increases towards the pole V has to decrease.
c> F = W  R
d> Stuck here. I presume that I have to use the equation from part C and gravity must be a factor but I am unsure of how to work this one out!
e> No idea how to work this out? Am I meant to google an equation for speed of rotation and the length of a day!? What would you do?