# Using Pivot Interactives Instead of Word Problems

While some of the activities in Pivot Interactives are intended to be in-depth explorations or model-discovery activities, others are meant for short in-class activities where students apply a physics concept to a concrete example. These are a valuable part of my teaching tool kit: several times per week students will work on an activity like this as an alternative to a word problem. Here are some examples.

**Using Pivot Interactives to Apply and Extend a New Concept**Sometimes students can make an observation on their own that deepens their understanding of a concept. For example, students can use two force sensors linked together to explore Newton’s Third Law force pairs. They’ll see that the reading on each force gauge is the same. But they are often left with the impression that this is only true for systems that are not moving. Ask them about what happens when a more massive object collides with a less massive one, and they often revert to their non-Newtonian preconceptions.

The Pivot Interactive activity Forces during Collisions allows students explore this phenomenon on their own. Students position a ruler to measure the deflection of hoops attached to air-track gliders as they collide.

Next, students select the mass and speed of each object, to see whether this affects the symmetry of the forces. Students are often very surprised by the outcome. It’s powerful learning when students explore and discover this for themselves.

This short activity takes no more than 15 minutes, either in class or at home, and gives students compelling evidence that interaction force pairs are symmetrical even in a collision between different mass objects moving at different speeds.

**Making and Testing Predictions: A Replacement for Word Problems**Traditionally, we use word problems to practice applying a model. Pivot Interactives has many activities that allow students to use measurements from a video to make a prediction, and then see whether the model yields accurate predictions. For example, students practicing using energy to analyze a system can use our magnetically-levitated puck for practice. In this video, the puck is flicked while coasting above the horizontal portion of the track. Students can measure the speed at which the puck moves along the horizontal portion, and use that to predict the height to which the puck will rise. Since there are 20 trials, students can (mostly) work on their own trial.

One of the things I like about this type of activity is the in-depth conversations students have while working on them. When we did this activity, I overheard two students talking about whether the puck was moving at a constant speed while it was on the flat portion. The decided that since they could not identify any forces causing the speed to decrease, they would *assume* it was moving at constant speed, and include their justification for the assumption in their submitted response.

Similarly, students had remarkable insights about the height measurements. They discussed the advantages of different Ug=0 locations. They discussed whether it is possible for an object or system to *have* gravitational potential energy hidden in some way even if the object is located at their chosen Ug=0 location. They discussed the different kinds of discrepancies: too high or too low, and discussed the different types of errors (measurement, calculation, or original assumption) that could lead to each one.

Here’s one more: students studying spring oscillators can predict the spring constant by measuring the period and knowing the mass on the oscillator. A second video allows students to measure the spring constant by watching the spring being compressed by various amounts of force. The data table and graphing tool let’s students make a graph to find the spring constant. This compact activity can be completed in less than 20 minutes, and is far more interactive and engaging than a word problem. Students enjoy finding out if physics works!

There are dozens of this type of activities on Pivot Interactives. They are fun, engaging, and useful ways for students to practice applying the models to real situations. These are not intended to replace labs. They are an engaging, realistic alternative to written word problems that evoke creativity and in-depth conversations about how simplified physics models are applied to real-world situations.

Find these activities by using the category filter. Under ** Activity type**, click

*Model Testing Using Prediction**, and press*

*Find**.*