Tutorial details

The tutorial begins with the same context as in the pretest. (The target blocks in the pretest, blocks B and C, are labeled blocks M and N in the tutorial.) Students are led to recognize that differences in the materials from which the target blocks are made can account for the differences in behavior. The tutorial helps students develop the principle of conservation of momentum by guiding them to draw relevant free-body diagrams and apply Newton’s second law to individual blocks. As they consider the forces exerted on the blocks and the accelerations of the blocks, students are led to recognize that the changes in momentum of the two blocks are always equal. They use this result to determine the ranking of the final speeds of the target gliders. The first part of the tutorial concludes with a student statement in which the fictional student treats momentum as a scalar quantity. Students respond to the statement on the basis of what they have done thus far in the tutorial.

In the second part of the tutorial, students treat the pair of blocks as a single system. They come to recognize that momentum conservation always applies for a system on which there is a zero net external force.

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Prerequisite tutorials

The Forces and Newton's second and third laws tutorials are prerequisites to Conservation of momentum.

Other prerequisites

Students should already have studied Newton’s laws and be familiar with the definition of momentum. They need not have studied momentum conservation.

Equipment

List

• white board or large sheet of paper with markers

Discussion