Pivot Interactives

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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.

 Students are not usually surprised that the forces are the same during collision of equal-mass objects moving towards each other at the same speed.

Students are not usually surprised that the forces are the same during collision of equal-mass objects moving towards each other at the same speed.

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.

 Students can select the masses and speeds of the gliders to try to find a combination that results in unequal interaction forces.

Students can select the masses and speeds of the gliders to try to find a combination that results in unequal interaction forces.

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.

 Students measure the speed of this magnetically-levitated puck as it travels leftward along the flat portion of the track. They use this speed to predict the height to which the puck will rise.

Students measure the speed of this magnetically-levitated puck as it travels leftward along the flat portion of the track. They use this speed to predict the height to which the puck will rise.

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.

 A second video is unlocked after students submit their prediction. This video shows the same event as their original video, but this time they can see the puck rise to its maximum height, allowing them to measure to test their prediction.

A second video is unlocked after students submit their prediction. This video shows the same event as their original video, but this time they can see the puck rise to its maximum height, allowing them to measure to test their prediction.

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.

 Pivot Interactives allows students to upload photos of their whiteboards as their response. This makes it easy to assess their thought process during class work.

Pivot Interactives allows students to upload photos of their whiteboards as their response. This makes it easy to assess their thought process during class work.

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!

 In this activity, students select a mass (133g-733g) and a spring configuration (single or double). They measure the period of oscillation and use it to predict the spring force constant.

In this activity, students select a mass (133g-733g) and a spring configuration (single or double). They measure the period of oscillation and use it to predict the spring force constant.

 Next, students use another video to measure the spring compression as 50g metal disks are placed on the spring.

Next, students use another video to measure the spring compression as 50g metal disks are placed on the spring.

 Students use the built-in data tables and graphing tools to analyze the data to measure the spring force constant. Does it match? Students seem to enjoy finding out if “physics works”.

Students use the built-in data tables and graphing tools to analyze the data to measure the spring force constant. Does it match? Students seem to 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.

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Peter Bohacek