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## Homework Statement

A 100g pendulum bob hangs from a 1 meter string. What is the tension in the string when the pendulum is not moving (i.e. at the 'bottom')? What is the tension when it is at 30° to the vertical?

## Homework Equations

100g=.1kg

g=-9.8m/s^2

F_t=-mgcos(Θ)

## The Attempt at a Solution

Tension when not moving:

F_t=-mgcos(Θ)=-(.1kg)(-9.8m/s^2)cos(0)=.98N

Tension at 30° to the vertical:

F_t=-mgcos(Θ)=-(.1kg)(-9.8m/s^2)cos(30°)≈.15N

Is that correct?

My main dilemma is that my professor told us when a pendulum exceeds a 15° swing angle, that it can no longer be considered a simple pendulum and goes by more complicated physics, however, this pendulum swings to twice that angle.

Also, when I put this on a different site, someone answered and said "The tension at any angle cannot be known unless you also know its velocity at that point."

Thoughts?