# Next-Time Questions

One of my favorite resources for developing conceptual understanding of physics are Paul Hewitt’s Next-Time Questions. Older ones are [hosted by Arbor Scientific](http://www.arborsci.com/Labs/CP_NTQ.aspx) and every month a new one is published in [The Physics Teacher](http://tpt.aapt.org/).

These questions often appear deceptively simple. However, a student’s first impression is often incorrect. I find that these are a great way to discuss and refine preconceptions. These questions are intended to be presented during one class and not discussed until the next. I always have students who are so excited to share their answer they are practically bouncing in their seats. I have to remind them that these are “next-time” questions and, therefore, we will discuss them the next-time we meet. I encourage them to discuss them with their friends over lunch or after school.

Hewitt implores us to use them as he intends:

Here is one that I recently used during the Balanced Force Particle Model unit.

The next time my class met, the discussion of this question consumed almost the entire class time. The discussion started with a review that the forces must be balanced since the book is at rest (the special kind of constant velocity where the velocity is zero). We practiced drawing the free-body diagram for the book which was a good review of the force of friction and the normal force. We were just beginning to explore vector components, and this was a great introduction since the force from the woman’s hand is directly both upward and to the right. We then debated if the force of friction should be directed upward or downward. Students had valid arguments for each. Another student asked if there was a force of friction at all. Eventually, we drew three different free-body diagrams for the cases where there is no friction, where there is friction directed upward, and where there is friction directed downward. A fantastic discussion all centered around a single drawing and simple question.

Some time ago, I reviewed every next-time question, downloaded those that aligned with concepts we cover, and copied them into unit folders so I would remember to use them when the time was appropriate. Now, I just review each month’s next-time question in The Physics Teacher and file it appropriately.

Give one a try in class. I think you and your students will love it.

## One thought on “Next-Time Questions”

1. geoff Post author

Jane Jackson shared a link to Paul Hewitt’s “60 questions Physics Students Should Know”:

http://www.arborsci.com/ConceptualPhysics/default.aspx

Hewitt writes, “Here are 60 questions on basic physics that you likely think your students can handle. But if you’re not focusing on the qualitative question sets in addition to problem sets in your algebra or calculus based introductory course, be prepared for your students to do poorly with these questions about basic content we take for granted. …”

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