 You need to describe the motion of a motor vehicle while you are driving  What factors affect ◦ Following distance ◦ Braking distance ◦ The total stopping distance SPEED AFFECTS ALL OF THESE!!!

Speed – the distance traveled per unit time Constant speed – speed that does not change over a period of time

 Model 1: Strobe photos  Model 2: Equations ◦ Average speed = (distance traveled)/(time elapsed) ◦ v av = Δd/Δt

Speed – the distance traveled per unit time Constant speed – speed that does not change over a period of time Average speed – the total distance traveled divided by the time it took to travel that distance

v av ΔdΔd ΔtΔt

 If you drive a distance of 400 mi (640 km) in 8 h, what is your average speed?

Speed – the distance traveled per unit time Constant speed – speed that does not change over a period of time Average speed – the total distance traveled divided by the time it took to travel that distance Instantaneous speed – the speed at a given moment

 You are traveling at 35 mph (~50 ft/s) and your reaction time is 0.2 s. Calculate the distance you travel during your reaction time. v av ΔdΔd ΔtΔt

 In an automobile collision, it was determined that a car traveled 150 feet before the brakes were applied. ◦ If the car had been traveling at the speed limit of 40 mph (60 ft/s), what was the driver’s reaction-time? ◦ Witnesses say that the driver appeared to be under the influence of alcohol. Does your reaction-time data support the witnesses’ testimony?

Speed – the distance traveled per unit time Constant speed – speed that does not change over a period of time Average speed – the total distance traveled divided by the time it took to travel that distance Instantaneous speed – the speed at a given moment Velocity – the speed in a given direction

 Model 1: Strobe photos  Model 2: Equations ◦ Average speed = (distance traveled)/(time elapsed) ◦ v av = Δd/Δt  Model 3: Graphs ◦ Distance-Time Graph

 Model 3: Graphs ◦ Distance-Time Graphs Graph 1 Graph 2 Graph 3 Graph 4

 Displacement – the difference in position between a final position and an initial position; it depends only on the endpoints, not the path; displacement is a vector quantity, it has magnitude (size) and direction

 Model 3: Graphs ◦ Distance-Time Graphs Graph 5 Graph 6 Graph 7 Graph 8

Reaction Distance – the distance that a vehicle travels in the time it takes the driver to react How is this related to Reaction Time?

 What is a safe following distance between your automobile and the vehicle in front of you? ◦ Speed: 55 mph (81 ft/s) ◦ Avg Reaction Time: 0.15 s ◦ Avg Car Length: 13 ft  How do you decide what a safe following distance is?

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 Driving at 1 sec distance, 2 sec distance and 3 sec distance Driving at 1 sec distance, 2 sec distance and 3 sec distance ◦

Claim: A distance-time graph will have a greater slope if an object is moving faster Evidence: Does your data support or refute this claim? Instructions: Make 2 graphs (rise: 50m; run: 10s). One will reach 50m in 10s, and the other will reach 25m in 10s

Study Guide:  Questions 8-15, Tutoring  Weekdays: 8:00AM  Mondays and Wednesdays: 3:45PM