1. Activity 82 Braking Distance
Challenge: How can friction lower the risk of getting into an accident?

2. Key Vocabulary:
Braking Distance: the distance the car travels after the driver applies the brakes, until the car comes to a complete stop.

3. Getting Started
In the next two activities you will examine the factors involved in slowing down a car to prevent an accident from occurring.
Read the Introduction on page 41

4. Car brakes cause a car to stop because of FRICTION.
Today, you will use a cloth to create friction between the cart’s wheels and the track.
When you cover the track with the cloth, will the cart’s braking distance become longer or shorter?

5. Doing the Activity Controlled Variables today: Changing Variables:
Braking surface
Mass
Vehicle shape
Changing Variables:
Starting height
Distance
Time traveled by the cart after breaking

6. Follow the procedure on pages 42-43.
Copy the data table on page 42 into your notebooks to record your results.
When you are finished, answer Analysis Questions 1, 2 and 4 in your notebooks.

7. Analysis Answers A. The cloth represents the brakes on a real vehicle
Strength’s
Weaknesses
Cloth slows the cart
Not representative of real brakes in a car

8. As the initial speed was increased, the braking distance also increased.
The faster a car is traveling, the more distance it takes it to come to a stop. This makes it more likely that a car will hit something.