Document Type

Instructional Material

Publication Date

7-2012

Abstract

Discovering Uniformly Accelerated motion is intended as a three week uniform acceleration unit taught weeks 4-6 in the context of a larger 9 week study on kinematics and Newton’s Laws in a regular level physics I course. Students are expected to have completed a unit on constant velocity motion and vectors prior to this unit. In addition, students are expected to have 8th grade level familiarity with forces (i.e. a force is a push or a pull). The unit is structured to allow students to uncover known relationships in a discovery fashion in an effort to keep this unit physics rather than algebra focused.

Because students experience motion in their everyday lives, through this experience, they often form misconceptions about motion that persist even after Physics I. Misconceptions such as “heavy objects fall faster than light objects,” “motion only occurs with an applied force,” and “gravity slows you down” are particularly persistent among my students. Thus, I elected to begin this unit by having students discuss and experience the difference between casual, everyday observation and careful experimentation when doing scientific discovery.

Students begin the unit from the historical context of Galileo’s experiments with the acceleration of gravity. First discussing why scientists argue that Galileo never dropped items off of the tower of Pisa, and then reproducing his inclined plane experiments and using graphical analysis to discover that:

1. In the absence of a force, relatively constant speed is maintained.

2. Distance traveled due to gravitational pull depends on a quadratic time function (acceleration)

3. This quadratic function (acceleration) is independent of mass

Having exhausted Galilean technology, we will introduce the term acceleration and use real time technology to then directly measure the acceleration of gravity and to gain further experience with motion graphs.

After ensuring that students understand the graphical representations of distance, velocity, and acceleration, students will revisit graphs to develop graphically based kinematics equation.

After a few days of practice with using kinematics equations, students will be tasked to develop a plan, including calculations, to accurately time the drop of a water balloon to intersect with an approaching constant velocity object (me). This performance task checks student ability to use constant velocity and uniform acceleration kinematics equations in a predictive manner as done in real world scenarios.

The unit ends with students learning further applications of kinematics in a 2 day series of projectile discovery activities focused on behavior and application of existing knowledge.

Unit goals include students:

1. Developing an understanding of the predictive nature of kinematics

2. Recognizing, testing, and then reconfiguring existing misconceptions about motion

3. Refining their understanding of the need for controlled experimentation in scientific discovery

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