Tutoring High School Student

Gamma

I am going to tutor a high school student. I had an initial meeting with him and learned that he is using Conceptual Physics by Paul Hewitt. During the initial consultation, the student had a few questions to ask. It was a typical problem where a mass on the table is attached to a string. The string passes over a pulley at the edge of the table. The other end of the string is attached to a hanging mass. Question is to find the acceleration of the masses. My immediate approach was to use Newton's second law to both masses and solve for acceleration. But the student has never learned how to draw force diagrams. He did not know about the tension on the string. This is my first experience with a high school student although I have college teaching experience. Is there any other approach to this problem?

Also, do you have any advice as to how to help high school students to learn and like physics? In two weeks, the boy has his mid-term test and he needs my help.

Thank you for any suggestions and advice.

Gamma.

Matterwave

I know of no simpler way of approaching this problem than to draw force diagrams. You can do it using Langrangian mechanics, but that'd be way over his head.

story645

Teach him how to draw force diagrams. It doesn't take that long and he needs to know how to do them for his exam (force diagrams show up in high school physics.) Look at how his textbook solves the problem and work from there. If it's in his textbook, that's the level he's supposed to be at.

Gamma

Thanks. His book did not have anything similar to this problem. But one of the end of chapter questions was similar to this one. But it had three diagrams with different mass combinations. In diagram 1, the hanging mass is larger than the one on the table. In diagram 2, masses were interchanged. In diagram 3, masses were same. Question was to compare the accelerations. Again, looking at this problem, it occurs to me that the student might not be expected to do the math. But, how else would you do this???

Gamma

story645

How does the chapter the problem is in approach the other problems in the chapter? Are there any formulas in the chapter? Ask to see his notes (hope he's taken some) and try to sort out how his teacher is teaching this.

The links on the book's webpage suggest using a free body approach.

Another idea is that it's an extension of the atwood machine problem 'cause the table is frictionless. Conceptual problems
about accelerating systems
pictures

I think you're basically supposed to do FBD's without calling them such. You think about "separable component forces" instead and push<->pull. The hanging mass pulls on the other mass, so it's causing the mass to move, but since they have a string connecting them they're moving at the same rate. So if one thing pulls another, how fast do they have to be moving? How do we know this? You're basically just explaining stuff without touching the math too much.

Moonbear

That was exactly my thought as I read the OP. He may need tutoring simply because he doesn't pay enough attention in class to know he's already been taught these basic essentials. And, if for some crazy reason they don't teach them free body diagrams in his class, it sure won't hurt to show him how to use them. If you're calling them "force diagrams," he may also not understand that is the same thing as a "free body diagram" which is what they are more typically called.