Distance traveled if a driver hits the brakes

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SUMMARY

The discussion focuses on calculating the distance a car travels when the driver applies the brakes. The driver is traveling at an initial speed of 51 km/h (14.2 m/s) and has a maximum deceleration of -6.0 m/s². Given that the yellow light lasts for 2.0 seconds and the car is 30 meters from the intersection, the key calculation involves determining how far the car will travel before coming to a complete stop. The solution requires applying the kinematic equations for uniformly accelerated motion.

PREREQUISITES
  • Understanding of kinematic equations in physics
  • Knowledge of units conversion (km/h to m/s)
  • Familiarity with concepts of acceleration and deceleration
  • Basic problem-solving skills in physics
NEXT STEPS
  • Study the kinematic equation: \(d = V_0 t + \frac{1}{2} a t^2\)
  • Learn how to convert speeds from km/h to m/s accurately
  • Explore examples of calculating stopping distances in physics
  • Investigate the effects of different deceleration rates on stopping distance
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Students studying physics, particularly those focusing on kinematics, as well as educators looking for practical examples of motion and deceleration calculations.

Naryeth
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Homework Statement


A person driving her car at 51 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning to red, and she is 30 m away from the near side of the intersection (Fig. 2-29). The intersection is 15 m wide. Her car's maximum deceleration is -6.0 m/s2, whereas it can accelerate from 51 km/h to 70 km/h in 5.7 s. Ignore the length of her car and her reaction time.

If she hits the brakes, how far will she travel before stopping (in meters)?

Homework Equations


I don't know. As far as I can tell, I have two unknowns here.

The Attempt at a Solution


Lost here. As far as I can tell, all I know is that V0 = 51km/h (or 14.2m/s) and a = -6.0m/s2. Any help is appreciated, thanks in advance.
 
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Naryeth said:
As far as I can tell, I have two unknowns here. All I know is that V0 = 51km/h (or 14.2m/s) and a = -6.0m/s2. Any help is appreciated, thanks in advance.
You also know that the car comes to a stop.
 

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