- #1
Specter
Homework Statement
Question:
Keys combined with a combined mass of 0.100 kg are attached to a 0.25 m long string swung in the vertical plane.
a) What is the slowest speed that the keys can swing and still maintain a circular path?
b) What is the tension in the string at the bottom of a the circle?
We are given:
m = 0.100 kg
r = 0.25 m
We need:
vminimum
Homework Equations
Fc = mv2 /r
Fg = mg
The Attempt at a Solution
My solution for part a which I think is correct:
Fc=mv2 /r
mg = mv2 /r
g = v2 /r
v^2 = g*r
v^2 = sqrt(9.8)(0.25)
v = 1.564 rounded 1.57 m/s.
Part b attempts:
I was told on another website to use conservation of energy but I haven't been taught that yet.
Attempt #1:
Fc = mv2 /r
Ft - mg = mv2 /r
Ft - (0.100)(9.8) = (0.100)(1.57)2 /0.25
Ft = 0.98 + 0.628
Ft = 1.608
Attempt #2:
Fc = mv2 /r
Ft-Fg = mv2 /r
Ft-mg = mv2 /r
Ft-g = v2 /r
Ft = v2 /gr
Ft = 1.572 /(9.8)(0.25)
Ft = 1.0 N
Attempt #3:
Fc = mv2 /r
Ft -mg = mv2 /r
Ft = mv2 /r + mg
Ft = (0.100)(1.57)2 /(0.25) + (0.100)(9.8)
Ft = 1.965 rounded to 2.0 N
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