Write the next sentence in this paragraph:

How to build and use a pendulum 
Collect your materials. 
This pendulum experiment is easy to do at home. All the materials should be readily available.
For the purposes of this article you'll only be doing one pendulum, but you can cut more of different lengths, so make sure that your length of string is over 70 centimeter (27.6 in). Gather two chairs and a meter stick.