Describe some basic guidelines for safe pre

PRE stands for progressive resistance exercises. This refers to exercises which progressively increase the load applied to the muscles. Here are some guidelines for safe PRE:

1. Do the exercises slowly, surely and smoothly. Avoid doing abrupt movements so as not to strain your muscles.
2. When doing the exercises, make your you execute them properly. For example, when lifting weights, lift them all the way up and all the way down.
3. Use spotters for support and to avoid accidents.

Sound energy is produced when an object vibrates. examples are 1- a balloon popping2-a whistle3- a waterfall