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Comparing Explicit and Implicit Teaching of Multiple Representation Use in Physics Problem Solving. Patrick Kohl, Noah Finkelstein University of Colorado, Boulder David Rosengrant Rutgers, the State University of New Jersey. Introduction – Multiple representations and problem solving.
Patrick Kohl, Noah Finkelstein
University of Colorado, Boulder
Rutgers, the State University of New Jersey
FR sphere on cart
FLsphere on cart
qrt sphere = -2.0 mC
qleft sphere = 1.0 mC
m = 2.5 kg
qcart = 5.0 mC
FEarth on cartExample problems
A small (100 g) metal ball with +2.0 mC of charge is sitting on a flat frictionless surface. A second identical ball with -2.0 mC of charge is 3.0 cm to the left of the first ball. What is the magnitude and direction of the electric field that we would need to apply to keep the balls 3.0 cm apart?
A sphere of 0.3 kg is charged to 30 mC. It is tied to the end of a rope and hangs 20 cm directly below a second chargeable sphere. If the rope will break at 4.8 N, what charge needs to be on the second sphere to break the rope?
Hint: It may be useful to draw a force diagram.
A frictionless metal cart is being held halfway between two stationary charged spheres. The cart’s mass is 2.5 kg and its charge is 5.0 mC. The left sphere has a charge of 1 mC and the right sphere has a -2 mC charge. The two spheres are 20 cm apart. At the instant the cart is released, what is the acceleration of the cart? Refer to the included diagrams for help.m = 2.5 kg
qcart = 5.0 mC10 cm20 cmqleft sphere = 1.0 mCqrt sphere = -2.0 mCFLsphere on cartFR sphere on cartFsurface on cartFEarth on cart
A 100 gram ball has a charge of 40 mC. The ball is dropped from a height of 2 m into a vertical electric field. As a result, the ball accelerates towards the floor at a rate of 7 m/s2. Draw a diagram showing all the forces involved in the picture, and calculate the magnitude of the electric field present.
*Parentheses indicate sample size N. N is the same for problems 1-3
Note: Forces were required as part of the answer for problem 4.
Fraction answering problem correct, and identifying 1, 2, or 3 forces correctly in solution. Note: Rutgers exam is multiple choice and CU quiz is free response.
Rutgers students construct complete FBD significantly (p = 0.0001) more often.
Student success as a function of number of forces correctly identified. Note that problem statement did not require an FBD.
1 D. Rosengrant, E. Etkina, and A. Van Heuvelen, National Association for Research in Science Teaching 2006 Proceedings, San Francisco, CA (2006)