A2L Item 162

• Description: Select the correct principle for efficient solution.
• Goal: Problem solving and developing strategic knowledge
• Source: UMPERG-ctqpe100
• Keywords: Problem Solving, Strategic Approach, Work-Energy Theorem

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The question for students:

You are given this problem:

{: .image-right } A mass m slides down a frictionless track of radius R=0.5m. Relative to the center of curvature, what is the angular acceleration of the mass as it reaches the bottom of the track.

What principle would you use to solve the problem MOST EFFICIENTLY.

1. Kinematics only
2. F = ma or Newton’s laws
3. Work-Energy theorem
4. Impulse-Momentum theorem
5. Angular Impulse-Angular Momentum
6. 1 & 2
7. 1 & 3
8. 2 & 3
9. none of the above
10. not enough information given

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Commentary for teachers:

Answer

(7) Students often think this problem requires angular momentum or angular dynamics. Many cue on anything circular. Some students may answer #10 thinking that the mass is needed.

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