Going Deeper with Newton’s Second Law and PASCO Smart Carts

I’ve been teaching physics for years and for most of the years that meant one thing: ticker tape.  Don’t get me wrong, there is a certain elegance to labs using ticker tape; there just isn’t as much depth.  Enter the PASCO Smart Cart and SparkVue software.

I’ve had the carts for a few years now and I keep learning more things to do with them.  I wanted students to go deeper into Newton’s laws but how could I do that with the Smart Carts and SparkVue?  Here’s what I came up with.

I took my old set-up from the ticker tape days.  Have a cart pulled across a table pulled by a hanging mass over a pulley. Change the amount of mass on the cart and the amount pulling the cart. Calculate the acceleration using kinematics.  Compare the mass times the acceleration to the weight hanging over the edge.

That set-up is lowish friction, which we could hand-wave away, but I never liked doing that.  If we used the carts on a track with the Super pulley would I get better results?  Indeed, I did. Measured accelerations were within 10% of theoretical. Could I do better?

I attached the hook to the carts and used the force sensor to measure the tension pulling the cart.  Using the data from the force sensor I got within 1% of expected values!  This is great accuracy and a starting point for going deeper.  Why does the force sensor start with the force of the hanging mass and then drop?  Why does the force sensor data give better data then using the values of the hanging mass?

The old lab changed the mass on the cart and the mass hanging off the edge to compare the effects of changing the mass of the system or changing the force of the system.  Good but not great. Now I can do the lab over the pulley or run the string through the end stop for increased friction.  The students can compare different variations of the set up in the same amount of time it took with the ticker-tape.

With ticker-tape it took a long time and didn’t go very deep; basic understanding only.  Now with the Smart Carts and SparkVue we can go deeper, quicker.  Isn’t that what we are after?  Critical thinking and deeper learning?  PASCO’s products offer a chance for that and I am grateful for it.