A2L Item 095
- Description: Determine the tension in a string wrapped around the disk and attached that holds a disk fixed on an incline.
- Goal: Problem Solving
- Source: UMPERG-ctqpe164
- Keywords: Forces, Mechanics, Problem Solving, Rotational Motion, Rotational Dynamics
The question for students:
A uniform disk with mass M and radius R sits at rest on an incline 30° to the horizontal. String is wound around disk and attached to top of incline as shown. The string is parallel to incline. The tension in the string is :
- Mg
- Mg/2
- 2Mg/5
- Mg/4
- None of the above
- Cannot be determined
Commentary for teachers:
Answer
(4) This problem can be solved a variety of ways. The simplest method is to balance torques about the contact point. This situation is an excellent one for discussing the advantages of thinking about preferred points about which to write the rotational dynamics equation.