# Circular Motion and angle alpha

## Homework Statement

A plumb bob is deflected from the vertical by an angle alpha due to a massive mountain nearby. (A) Find an approximate formula for alpha in terms of the mass of the mountain the distance to its center and the radius and mass of the earth
(B) Make a rough estimate of the mass of mt everest assuming it has the shape say of an equilateral pyramid or cone 4k m above its base and then (c) estimate the angle alpha of the pendulum bob if it is 5 km from the center of mt everest

## Homework Equations

F= G*m1*m2/r^2

G = 6.67*10^-11

shoot idk throw some vector equations in there too

## The Attempt at a Solution

well...i said
Mm = mass of mountain
m = mass of bob
Dm = Distance to mountain from bob
Fm = force exerted by mountain on bob
Me = Mass of earth

Fm = G*Mm*m/(Dm)^2
g = G*Me/(Re)^2

i made a right triangle with vector mg, vector Fm and hypotnuse of the deflected bob string

using trig i got alpha = 90 - theta where tan(theta) = mg/Fm

I know this can't be anywhere near to right...and i dont want to attempt other parts before i get this...PLEASE HELP!!!!!!

Last edited:

Dick
Homework Helper
That's right, if you really mean alpha=90-theta where tan(theta)=mg/Fm. Then tan(alpha)=Fm/mg.

Ok now can anyone help me figure out B....that is if i got A correct. I really honestly have no idea what they want me to do for B. Idk if im supposed to look up values for this or what (i can find a rough volume of it i suppose but its not like i know the base or anything) I am certain there is NO more info on the question

PLZ HELP!!!

Dick