I borrowed this idea that I originally saw from @rutherfordcasey and @kellyoshea. I am always thinking about ways for students to collect data and to be able to assess their methods using that data. So I decided to time the finish using two force plates, allowing us to quantify the race. This turned out to be a rewarding lab practical midway through our Newton’s 2nd Law unit.
The students received a fairly simple set of questions to guide them through the process and to give me something substantial enough to assess their understanding.
Newton’s 2nd Law
- Using the setup at the front of the room calculate where the two carts must start from in order to hit the force plate at the bottom of the ramps at the same time. The carts must travel a minimum of 1.0 m. Show all of your work in a neat and well organized manner below. You must provide some narrative to describe what you are solving for in each step.
- Test your calculations. How far off are you, is it within an acceptable amount of error?
- If the two carts do not hit at the same time, within an acceptable amount of error, re-evaluate your solution and perform the test again.
- What sources of error exist in this experiment so that your theoretical values do not match what actually happens?
In small groups the students worked through the solution and began testing. They also learned how to measure the angle of an incline using a protractor and plumb bob.
The 1.0 m minimum forced them to put more thought into the kinematics of the carts’ motion which was a great review of prior material. After calculating and running their tests all groups were able to get great data, with the carts hitting within 0.10 s of each other.