# bead on string circular motion (1 Viewer)

#### erucibon

##### Member

For this setup, if I have calculated the velocity, know the mass of the weight and radius, how can I calculate the mass of the bead?

Thanks

#### Drdusk

##### π
Moderator
View attachment 27486
For this setup, if I have calculated the velocity, know the mass of the weight and radius, how can I calculate the mass of the bead?

Thanks
What are your thoughts? Have you got any working out you could show us, doesn't matter if it is wrong. =)

There's no point if were doing it all for you.

#### StudyOnly

##### Active Member
Think about what is causing the centripetal force and equate it to Fc.

#### erucibon

##### Member
What are your thoughts? Have you got any working out you could show us, doesn't matter if it is wrong. =)

There's no point if were doing it all for you.
I am thinking that since Fnet = Fc = mv^2/r, and the mass on the bottom also experiences the Fnet = Ma, mv^2/r = Ma. I'm not sure if this is right, because I'm confused on where the tension and weight force on the bead goes?

#### Drdusk

##### π
Moderator
I am thinking that since Fnet = Fc = mv^2/r, and the mass on the bottom also experiences the Fnet = Ma, mv^2/r = Ma. I'm not sure if this is right, because I'm confused on where the tension and weight force on the bead goes?
Your on the right track, the question does involve the Fc and Tension and what not, but why would the mass on the bottom experience Fnet? The mass on the bottom is stationary and it provides the Tension force of the string(hint: You need to use this).

#### erucibon

##### Member
Your on the right track, the question does involve the Fc and Tension and what not, but why would the mass on the bottom experience Fnet? The mass on the bottom is stationary and it provides the Tension force of the string(hint: You need to use this).
Is it because tension is the force causing centripetal force, and tension is equal to Mg, so Mg = mv^2/r?

#### StudyOnly

##### Active Member
Is it because tension is the force causing centripetal force, and tension is equal to Mg, so Mg = mv^2/r?
That's correct, just rearrange and solve