If you pull down on a mass that hangs from a spring, it will bounce up and down for a while before stopping. why does the mass bounce?

All spring have what is called a 'spring constant'. This 'spring constant' tells us how strongly the spring wants to go back into its regular position if it is stretched or compressed. So, if you pull on a spring and let go, it will pull back to its regular position, except it will go a little farther than its resting place, so the spring pushes back against the compression and the force will cause the spring to stretch again, but this time not as far as you pulled it. This process repeats until the stretching followed by compression becomes smaller and smaller until it appears to be settled.

Hope this helps you understand! Good luck!

The objects do not reach terminal velocity         there is not enough time from the time the object falls from when it hits the ground to achieve terminal velocity. an object must be placed higher to achieve terminal velocity in order to be in free fall.