A2L Item 103
- Description: Identify the correct motion of a spool pulled by a string passing at an angle to the bottom of the central axle.
- Goal: Reason with rotational dynamics.
- Source: UMPERG-ctqpe138
- Keywords: Mechanics, Rotational Dynamics, Torque
The question for students:
A spool has string wrapped around its center axle and is sitting on a horizontal surface. If the string is pulled at an angle to the horizontal when drawn from the bottom of the axle, the spool will
- roll to the right.
- not roll, only slip.
- roll to the left.
- cannot be determined.
Commentary for teachers:
Answer
(4) The motion of the spool depends upon the angle θ. When the line of action of the force passes through the contact point the spool will slide and not rotate. At lower angles it will roll to the right and at higher angles it will roll to the left.