Linear Motion Lesson

Content Area: Physics (11-12)
Topic: Kinematics
Sub-Topic: Linear Velocity and Acceleration

Computer requirements: Vensim or STELLATM, IP physics, Excel or Internet access
Prior content covered: None
Estimated time for computer portion of lesson: 60 min

Essential Questions or Ideas to address:

• How are velocity and acceleration different?
• How are velocity and acceleration related?
• How do we interpret graphs of motion in terms of velocity and acceleration?

The lesson (90-min block): In the first half- hour, students build a basic constant velocity model and explore the effects of changing the initial position or the velocity on the position-time and velocity - time graphs produced. This model is a basic introduction to Vensim or STELLATM icons and the graph output. The model can also be used to model data collected in class.

In the second half-hour, students add acceleration to the model and again explore the effects of changing variables on the graphs produced. This basic acceleration model is at the heart of many future models. For more details, see the Simple Kinematics Activity Packet.

• Objects at rest cannot be accelerating.
• Velocity and acceleration must be in the same direction.
• Same position means same speed
• Velocity must be positive
Evaluation of lesson effectiveness:  The primary purpose of this lesson is to introduce students to Vensim, STELLATM or another modeling environment while the content is fairly simple.  However, if the activities and follow-up questions are crafted carefully enough, many student misconceptions can be addressed early on.  In addition, students can be exposed to a variety of graphs in a short time and begin to build their graph interpretation skills.

Alternate presentation:  It is easy enough to build one or more Excel worksheets that allow students to explore the variables and their effect on various graphs.  All that is lost is the visible relationship between  those variables which can be inferred from the Vensim/STELLATM model.  This relationship could be emphasized through a concept map.

It is also useful to explore velocity and acceleration using an Interactive Physics program or web-based applet.  In this case, students can actually observe the particles moving and if a trace function is used, it help students distinguish position from velocity and to readily see the effects of velocity and acceleration on movement. An interactive physics model can be found at: http://www.interactivephysics.com

Math topics: Linear and quadratic equations, graph interpretation for those equations

Standards:

MSDE (from the website as of 9/05):

 Physics/Core Learning Goals Science Indicator 5.1.2 The student will use algebraic and geometric concepts to describe an object's motion. Assessment Limits direction, position, distance/displacement, speed/velocity, motion with a constant acceleration, one and two dimensional motion, frames of reference Goal 5 Concepts Of Physics The student will demonstrate the ability to use scientific skills and processes (Core Learning Goal 1) to explain and predict the outcome of certain interactions which occur between matter and energy. Expectation 5.1 The student will know and apply the laws of mechanics to explain the behavior of the physical world.

The standards do not directly address kinematics, but an understanding of motion is necessary before students can address the standards as they appear here.

National Science Standards:

Physical Science: Motion and Forces:
Objects change their motion only when a net force is applied. Laws of motion are used to calculate precisely the effects of forces on the motion of objects. The magnitude of the change in motion can be calculated using the relationship F = ma, which is independent of the nature of the force.  Whenever one object exerts a force on another, a force equal in magnitude and opposite in direction is exerted on the first object.

AAAS Benchmarks:

The Physical Setting: Forces of Nature:

• The change in motion of an object is is proportional to the applied force and inversely proportional to the mass.
• All motion is relative to whatever frame of reference is chosen, for there is no motionless frame from which to judge all motion.

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