If the spool is pulled horizontally to the right. in which direction will it roll? to the left? to the right? others ...
	Think about it！！！ And explain why ? What if it is pulled in the following way? Want to know the answer ? Try the following java applet! Or find a spool and check it out?

You need to answer the question first in order to start the animation. Pick an answer!

Press Reset for default parameters.

You can click near the top of the green region and drag it up and down.

Try it with different height!

During the animation, click the left mouse button to suspend the animation.
Click it again to resume.