Content Area: Physics (1112)
Topic: Kinematics
SubTopic: Tailgating
Computer requirements: Vensim, STELLA^{TM}, or Excel
Prior content covered: Linear velocity and
acceleration
Estimated time for computer portion of lesson:
30  60 min
Essential Questions or Ideas to address:
 What is a good rule for safe following distances?
 How do model assumptions affect model outcomes?
The lesson (90min block): Students build or
manipulate a prebuilt Vensim or STELLA^{TM} model which is based on the braking
distance model but now involves two cars. For a range of
velocities, students try to find the minimum safe following distance
for a particular set of braking conditions. Depending on
time alloted, each student can be assigned one velocity and the whole
class can explore only one acceleration. Or each student can
explore the whole range of velocities for a particular
acceleration.
After the data is collected, students compare their
model results to the safe following rules learned in driver's education
classes. Students can then discuss model assumptions and variables
which can effect the results. For more details, see the Tailgating Activity Packet.
Sample output assuming different following distances may be found at A Comparison of Tailgating Scenarios.
Common misconceptions addressed:
 For a given acceleration, the relationship between
initial velocity and braking distance is linear.
Evaluation of lesson effectiveness:
Like braking distance, this can represent a powerful connection
between classroom learning and the "realworld". Students do
struggle with the graph interpretation, but teachers could modify the
model output to simplify the graphs.
Alternate presentation: This activity
was originally described as a spreadsheet activity in The
Physics Teacher (R. C. Nicklin, "Kinematics of Tailgating", February 1997 , Volume 35, Issue 2, pp. 7879) .
Math topics: Linear and quadratic equations,
graph interpretation for those equations, using a graph to determine
events, data collection and analysis
Extensions: Students can investigate other
variables in the model, such as reaction time and braking acceleration
as they relate to driver awareness or road conditions. Students
could prepare safety posters or lessons based on their findings.
Drunk Driving and Tailgating illustrates the
impact of blood alcohol concentration on the driver's reaction time.
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.
