# Radial acceleration in a pendulum

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1. Dec 4, 2014

### Sam Smith

I'm just trying to think how I would expect radial acceleration to look like in a pendulum. I would expect a sine wave of sorts but instead of oscillating around zero I would expect it to be around a positive number as this acceleration is always in the same direction. Also if I was to compare this to the tangential acceleration it would have the same freq but as I say, be in the positive direction. Just wanted to check my reasoning?

2. Dec 4, 2014

### Sam Smith

Well I am thinking more specifically of the rotating frame (I know in the inertial frame the radial acceleration changes direction) (ie fixed on the pendulum bob itself) So if you exclude gravity I am wondering what the acceleration trace would typically look like? Or perhaps its better known as centripedal acceleration?

3. Dec 4, 2014

### Staff: Mentor

Hi Sam,

Sorry, I deleted my reply right after I posted it, since I got the terms radial and tangential backwards in my reply. Here is a pretty good web page with animations of velocities and accelerations for pendulums:

http://www.physicsclassroom.com/class/waves/Lesson-0/Pendulum-Motion

:-)

4. Dec 4, 2014

### Dr.D

Why don't you simply work it out? There is no need to be dependent on the work of others if you simply exercise your brain and figure it out for yourself.