SS Day 6: Getting Newton’s 2nd Law

Monday, 23 June 2014


Pulling a cart at constant force is tough!

Tried something new today, based heavily off of labs from Frank and Kelly, which I understand is important in the unbalanced forces model. You need a motion detector, a dynamics cart, a bunch of masses, a spring scale, and some room to run. The result I liked best was seeing position-time graphs like these kids got. Did you see that? Check it:


We struggled with one detail, however: pulling with constant force. How can I get the kids to consistently pull with a constant force? We were just pulling and watching the spring scale.

This lab still needs some work from me but it was a great start, especially for the fourth Monday of summer school.


2 thoughts on “SS Day 6: Getting Newton’s 2nd Law

  1. You need much weaker springs and/or much more mass to pull with constant force. When we do this lab, we use long PASCO spings and stretch then half a meter using a ruler. We also use these larger dynamics carts and then stack the bricks on the carts. This gives reliable results. Because the spring constants of the spring scales are so large, even small changes in stretch produce noticeable changes in the force exerted by the spring.

    One other experiment that has worked really well for me with the PASCO carts is to use the fan cart attachments, and change the number of batteries in the fans.

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