Discovery Labs in Physics

Transformation of Intro Labs We have used an NSF CCLI matching grant to transform intro physics labs from “cookbook” to “discovery” format.

Cookbook Labs The “cookbook” lab manual directs the student through the lab. The student is basically a technician rather than a scientist.

SHM - Cookbook Lab Notebook. Keep notes for this experiment in your lab notebook. Data Acquisition. Use M in the range from 50 g to 500 g. Include the mass of the mass holder in the value of M. To get an accurate value of T measure the time for 20 periods. (Note: begin the count at the end of the first period.) Be sure that you estimate the uncertainties in both T and M.

SHM – Cookbook (2) Data Analysis. Plot T 2 (on the y-axis) vs. M (on the x-axis). Find the slope of this line and the uncertainty in this value. Find the y-intercept of this line and the uncertainty in this value. Write the experimental equation which relates T 2 and M.

SHM – Cookbook (3) Results. Based on the linear fit values, what is the experimental value of k and its uncertainty? What is the physical meaning of the y-intercept, b?

Motivation for Change Brightest students considered the course to be boring. Course did not help develop conceptual understanding. Course did not develop critical thinking.

Discovery The “discovery” method involves the student actively in the learning process. The student does science.

Discovery Student-centered. Develop conceptual understanding. Develop critical thinking. Encourage experimentation and imagination. Encourage teamwork.

Discovery – Pre-Lab The pre-lab exercise introduces students to the basic theory. Physical Pendulum. The period of a physical pendulum for small angles is given by the following equation: Period = 2  (I/mgd) 0.5 where m is the mass of the pendulum, d is the distance between the center of mass and the center of rotation, and I is the moment of inertia about the center of rotation.

Discovery - Prediction Before making measurements, students are asked to make predictions Consider a physical pendulum made up of two identical masses connected to a low-mass rod. The pendulum rotates about the center of the low-mass rod. center of rotation d2d2 d1d1

Discovery - Prediction These predictions are recorded as part of the experiment In your lab notebook, describe how the period will change as d 2 is increased. Assume d 1 is at its maximum value. Explain why the period changes in this way center of rotation d2d2 d1d1

Discovery - Measurement Measurements are made to test the predictions. Set the lower mass near its lower end (i.e. d 1 equals 18 cm) and the upper mass just below its upper end (i.e. d 2 equals 17 cm). Measure the period of oscillation for small angles. Repeat the period measurement for two other positions of the upper mass. Record the values of d 1 & d 2 and the measured period in your lab notebook.

Discovery - Analysis Students compare predictions and measurements to test their understanding of the physical phenomena. In your lab notebook, compare calculated and measured values of the period of this physical pendulum. Do the predicted and measured values agree?

Conclusion - Pros More interesting. Students learn concepts better. Students get more hands on experience. Greater instructor satisfaction.

Conclusion - Cons Less graphical analysis. More work for instructors. Appropriate hardware and software is required.