The Physics of Stopping: Mercedes Commercial 80 mph in 4 Sec

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SUMMARY

The discussion centers on the physics behind a Mercedes commercial claiming a car can stop from 80 mph in 4 seconds. It is established that stopping distance is influenced by the friction coefficient between the tires and the ground. With a speed of 80 mph translating to 117 feet per second, the average speed during deceleration is 58.7 feet per second, resulting in a stopping distance of 235 feet. To achieve a deceleration of 20 mph per second, a friction coefficient of 0.95 is required.

PREREQUISITES
  • Understanding of basic physics concepts, particularly motion and deceleration.
  • Knowledge of friction coefficients and their impact on stopping distance.
  • Familiarity with speed conversion (mph to feet per second).
  • Basic calculations involving average speed and distance.
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  • Research the physics of deceleration and stopping distances in vehicles.
  • Explore the role of tire materials and their friction coefficients in vehicle performance.
  • Learn about the equations of motion, specifically those related to constant acceleration and deceleration.
  • Investigate real-world applications of stopping distance calculations in automotive safety standards.
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Automotive engineers, physics students, safety analysts, and anyone interested in the mechanics of vehicle stopping distances.

krehbester
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There's a Mercedes commercial that claims one of their cars can stop from 80 mph in 4 seconds. My question is: if you stop any object moving at 80 mph in 4 seconds will it always take the same distance to stop no matter the size or weight? If so how far?
 
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If they give you the time and speed, the size and weight are already accounted for.

80mph is 117 fps. Assuming constant deceleration, the average speed is 58.7fps and therefore the distance is 235 ft.

The primary factor in stopping distance is the friction coefficient of the tires/ground. In this case, to decelerate by 20mph every second, you need a friction coefficient of .95, as g is 21 mph/s.
 

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