(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

a 0.12kg mass is suspended on a magic string with no mass, and length of 0.80m. There is no air resistance, and the pendulum is swinging such that it makes a maximum angle of 45 degrees with the vertical.

A.) What's the speed as it passes the vertical position?

B.) What is the tension in the string when it makes an angle of 45 with the vertical?

C.) What is the tension in the string as it passes through the vertical?

2. Relevant equations

3. The attempt at a solution

A.) I simply used the conservation of energy to determine it's velocity at the bottom:

[tex]mgh = \frac{1}{2}mv^{2}[/tex]

[tex]gh = \frac{1}{2}v^{2}[/tex] //masses cancel

[tex]\sqrt{2(9.8)h} = v[/tex]

[itex]h = (.80)-(.80)cos(45)[/itex]

[tex]\sqrt{2(9.8)((.80)-(.80)cos(45))} = v[/tex]

[tex]v=2.1 m/s[/tex]

B.) Here is what I tried:

[tex]T = \frac{mg}{cos(45)}[/tex]

[tex]T = \frac{(0.12)(9.8)}{cos(45)}[/tex]

[tex]T = 1.66 N[/tex]

Which is wrong for some reason. I believe the solution to be mgsin(45) but I don't understand why?

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# Homework Help: Tension on a string during SHM

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