# Simple Harmonic Motion Pendulum problem

bobbricks

## Homework Statement

A simple pendulum of length =30.0cm is released from rest from an angle of θ=10.0∘ to the vertical.
Assuming that the pendulum undergoes simple harmonic motion, find its maximum speed.

Source: https://isaacphysics.org/questions/accuracy_shm_pendulum_num

## Homework Equations

a) v=wA
b) T=2pi*root(L/g) --possibly?

## The Attempt at a Solution

A=0.3-0.3cos10
w=2pi/T
so w=root(g/L) by subbing equation a) into b).
g=9.81 and L=0.3.

so v=root(9.81/0.3)*(0.3-0.3cos10)
=0.02606... ms^(-1)

But that isn't the correct answer?

## Answers and Replies

Staff Emeritus
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A is the amplitude of oscillation, not the length of the pendulum.

bobbricks
Is A=0.3-0.3cos10 ?

bobbricks
Bump

Staff Emeritus
Homework Helper
Gold Member
2021 Award
Is A=0.3-0.3cos10 ?

How did you come up with this number? How far away from the equilibrium is the pendulum when it is at an angle of 10 degrees?

bobbricks
Its maximum velocity will be at the lowest point. The total length is 0.3m. Its current vertical height distance from the top is 0.3cos10. So the difference is 0.3-0.3cos10 which is the maximum amplitude..?