Learning, retention, and forgetting of Newton’s third law throughout university physics

We present data from a between-student study on student response to questions on Newton’s third law given in two introductory calculus-based physics classes (Mechanics and Electromagnetism) at a large northeastern university. Construction of a response curve reveals subtle dynamics in student learning not capturable by pretesting and post-testing. We find a significant positive effect of instruction that diminishes by the end of the quarter. Two quarters later, a significant dip in correct response occurs when instruction changes from the vector quantities of electric forces and fields to the scalar quantity of electric potential. When instruction returns to vector topics, performance rebounds to initial values.

Figure 1

Student participation is bimodal, with 40% of students completing seven or more tasks, and $\sim 30\%$ of students completing less than three.

Figure 2

Generally, women participate more often than men. The course is about 70% male.

Figure 3

Phase 1 prompt and responses for N3L task for Mechanics. The students were asked to consider situations where the car was speeding up, constant speed up a hill, constant speed on a level road, and slowing down. In each case, the force that the car exerts on the trailer is equal and opposite to the force that the trailer exerts on the car.

Figure 4

Phase 1 prompt and response for N3L task for E&M. The students were asked to compare the forces on the rod and ball for the three scenarios where the ball started to move, sped up, slowed down, and at rest at the apex of the swing. As in the mechanics example, the forces in each case are equal and opposite.

Figure 5

Response curve for Mechanics. Before instruction response could be chance. There is a broad peak during instruction with a maximum during week 6 which is the end of the section on forces.

Figure 6

Response curve for E&M. The response is mostly flat around the average of 66% with a measurable dip during week 4. This dip corresponds to the period of instruction in electric potential.