Why Is Calculating the Centripetal Force in a Bohr Atom Challenging?

[veloix]

Homework Statement

In the Bohr model of the hydrogen atom, the speed of the electron is approximately 2.00 x 10^6 m/s.
(a) Find the force acting on the electron as it revolves in a circular orbit of radius 5.50x 10^-11 m

Homework Equations

∑fy=ma=mv^2/r
ac=v^2/r

The Attempt at a Solution

i am always magnitude orders off for the force and don't know why, when do free body the only force i can think of that acts on the electron is the centripcal acceleration due it a ciclulr orbrit. looking in the book the mass of a hydrogen atom is 1.67x10^-27.
∑fy= (1.67x10^-27)(2x10^6)^2/(5.50x10^-11)
= 1.21x10-4 N but this wrong can some help me understand this better.

 

[PhanthomJay]

You are incorrectly using the mass of the atom. What mass should you be using?

 

[veloix]

atomic mass
?

 

[veloix]

ah the mass of the electron

 

[PhanthomJay]

ah the mass of the electron

yes...!

 

[veloix]

but i still get the wrong answer.

 

[veloix]

fy=mv^2/r+mg
Fy=(9.108*10^-31)(2*10^6)^2/(5.5*10^-11)+(9.108*10^-31)(9.80)
= 6.6*10^-8
still off by magnitudes i don't what to do

 

[PhanthomJay]

fy=mv^2/r+mg
Fy=(9.108*10^-31)(2*10^6)^2/(5.5*10^-11)+(9.108*10^-31)(9.80)
= 6.6*10^-8
still off by magnitudes i don't what to do

The centripetal force is primarily delivered by the electromagnetic force between the positively charged proton and negatively charged electron. But no matter what the source is for the force, what's the formula for centripetal force?