Can You Pull a String Without Producing Torque?
1. Place a spool of string or thread on a table. For best results, use a
spool with rims noticeably wider than its axle.
2. Pull gently on the string or thread so that the spool rolls without
skidding and its gain in rotational speed is directly proportional to
the torque.
3. Predict the effect of pulling the string both ways—with the string
on the top and with the string on the bottom.
4. Think Is there an angle at which the string can be pulled that will
produce no torque?