82 Braking Distance

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82 Braking Distance Key Vocabulary braking distance controlled variable tested variable variable

82 Braking Distance Read the introduction and look for key ideas Car brakes

82 Braking Distance How can friction lower the risk of getting into an accident?

82 Braking Distance Braking distance Braking distance is the distance a vehicle travels in the time between the moment the brakes are applied and the moment when the vehicle comes to a stop is the braking distance.

82 Braking Distance Review the procedure When you cover the track with the cloth, will the cart’s braking distance become longer or shorter?

82 Braking Distance Complete the procedure and record your data

82 Braking Distance Summarize your results What basic trend do you see the data? Share your answers with the class.

82 Braking Distance Analysis question 1 In this model of a stopping car: a.What does the cloth represent? b.List some strengths and weaknesses of this model.

82 Braking Distance Analysis question 2 What effect does speed have on braking distance? Explain, using evidence from this activity.

82 Braking Distance Analysis question 3 Does the evidence you gathered in this investigation support the statement below? Explain why or why not, using evidence from your investigation. A car moving at 55 mph needs less distance to stop than an identical car moving at 45 mph.

82 Braking Distance SCORING GUIDE: Recognizing Evidence

82 Braking Distance Analysis question 4 Reflection: Why do you think excessive speed is a factor in about 20% of fatal car accidents?

82 Braking Distance Conclusion Higher speed means it takes longer to stop a car. Higher speed on impact means a larger force on the occupants.

82 Braking Distance How can friction lower the risk of getting into an accident? How are car brakes related to friction?

82 Braking Distance Key vocabulary definitions Braking distance - The distance a vehicle travels from the time the driver applies the brakes until the vehicle comes to a complete stop. Controlled variable - A variable in an investigation or experiment that is held constant.

82 Braking Distance Key vocabulary definitions Tested variable - A variable that is changed in a systematic way in an experiment or investigation in order to determine its effect. Variable - A factor in a scientific experiment that can vary.

82 Braking Distance Compare data Post your results on the Issues and Physical Science page of the SEPUP website, and compare your data sets to those of students in other classes.