Question
A piece of rubber under an ordinary stress can display 100% strain; yet when unloaded, it returns to its original length. Does this show that the restoring forces in a rubber piece are strictly conservative?
Solution
In case of rubber, the loading curve of stress versus strain graph does not coincide with unloading curve because of elastic hysteresis. Hence work done by restoring force over one complete cycle of loading and unloading is not zero. Hence restoring forces in a rubber piece are not conservative.
