Skidmarks

By Bartley Richardson •

Grade Level	11th and 12th
Subject Area	Physics (Mechanical Physics)
Duration	70 minutes (one class period)
Setting	Classroom
Background Knowledge	It is recommended that studnets have some experience with Newton's First and Second Laws of Motion, motion at constant acceleration, solving the quadratic formula, finding the slope of a line, and reading a graph.
Author	Bartley Richardson

Summary
IThis activity reinforces the concepts of velocity, acceleration, friction, motion (Newton's First and Second Laws), and slope (grade). It also requires students to be able to read a graph (speed nomograph) and make inferences on their observations. Students measure given skidmarks, calculate the coefficient of friction between the tires and the road, calculate the grade of the road, and use this information to determine how fast a vehicle was traveling when it started braking.

Objectives
Students will be able to Calculate the coefficient of friction for a given object. U nderstand how friction acts on an object in motion. M easure distances on a scale drawing and translate those measurements to a larger scale. C alculate percent grade (slope), correctly define its meaning, and be able to interpret how it effects the motion of an object. Calculate the velocity (speed) of an object by using the speed nomograph. C onvert between metric units and from US to metric measurements. Use the quadratic formula to solve for a given variable. Identify real-world applications of physics principles. Identify, define, and correctly use Newton's First and Second Laws of Motion.

Materials Required
• Skidmarks – An Accident Report Packet • Step-by-step instructions • Speed nomograph • Worksheets / data tables • Ruler or other straight-edge • Grading rubric

Ohio Standards
Science Physical Science Benchmark D - Apply principles of forces and motion to mathematically analyze, describe, and predict the net effects on objects of systems. Science and Technology Benchmark A - Predict how human choices today will determine the quality and quantity of life on Earth. Scientific Inquiry Benchmark A - Make appropriate choices when designing and participating in scientific investigations by using cognitive and manipulative skills when collecting data and formulating conclusions from the data. Mathematics Geometry and Spatial Sense Benchmark A - Use trigonometric relationships to verify and determine solutions in problem situations. Patterns, Functions and Algebra Benchmark B - Use the quadratic formula to solve quadratic equations that have complex roots.