Circular motion and speed of rotation

[kikifast4u]

Homework Statement

There's a 'chair-o-plane' with a radius of 4m and the seats are connected using 3m chains.
a) Calculate the speed of rotation at which the chains make an angle of 35 to the vertical
b) What is the tension in the chain if a rider of 90kg is on the swing at the speed above?

Homework Equations

Newton's laws, Centripetal force formula, Trigonometric formulas

The Attempt at a Solution

I did a) and found a reasonable value of about 11RPM.
However I have a problem with b).
I get to equations, T'*sin(35)=g(M+m) and T'*cos(35)=a(M+m), where T' is the tension and M and m are the masses of the rider and the chair. Since I have a=g*tan(35) (from a) ), the two equations above are equivalent and I therefore have one equations with two unknowns. Am I missing something? How can I get m in order to find T'?

 

[tiny-tim]

hi kikifast4u!

There's a 'chair-o-plane' with a radius of 4m and the seats are connected using 3m chains.
a) Calculate the speed of rotation at which the chains make an angle of 35 to the vertical
b) What is the tension in the chain if a rider of 90kg is on the swing at the speed above?
…
I get to equations, T'*sin(35)=g(M+m) and T'*cos(35)=a(M+m), where T' is the tension and M and m are the masses of the rider and the chair. Since I have a=g*tan(35) (from a) ), the two equations above are equivalent and I therefore have one equations with two unknowns. Am I missing something? How can I get m in order to find T'?

i think you're supposed to assume that the mass m of the chair is negligible compared with the mass M of the rider, ie that m = 0

 

[kikifast4u]

I do hope so. Otherwise I don't think I have enough data to get a numerical value. Thanks!

 

[Pr.George]

kikifast4u,
This is professor George, i believe by signing the Own Work declaration you agree not to use the help of any external agency to solve your Assignments.
This is viewed by the university as a serious offence.
I had a look at your paper and i already got your name, your assignment won't be corrected or graded unless you head to the ETO and confess you used external help.
Failure to do so will result in more than losing grades.
Thank you.