Question about constant acceleration

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SUMMARY

The discussion focuses on a physics problem involving constant acceleration while driving. The scenario describes a car traveling at 20 m/s, 110 m from an intersection when the light turns red, with a reaction time of 0.50 seconds. The user successfully calculates the distance from the intersection when braking begins as 100 m. The main queries involve determining the necessary acceleration to stop at the intersection and the time required to come to a complete stop.

PREREQUISITES
  • Understanding of kinematic equations for constant acceleration
  • Familiarity with basic physics concepts such as velocity, acceleration, and reaction time
  • Ability to manipulate algebraic equations
  • Knowledge of the formula for distance traveled under constant acceleration: d = v_i * t + 0.5 * a * t^2
NEXT STEPS
  • Research the kinematic equations for uniformly accelerated motion
  • Learn how to calculate acceleration using the formula a = (v_f - v_i) / t
  • Study the concept of reaction time and its impact on stopping distance
  • Explore real-world applications of constant acceleration in driving scenarios
USEFUL FOR

Students studying physics, educators teaching kinematics, and drivers interested in understanding braking dynamics and safety measures.

elizabethR
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how would i do this problem...

You are driving to the grocery store at 20 m/s. You are 110 m from an intersection when the traffic light turns red. Assume that your reaction time is 0.50 s and that your car brakes with constant acceleration.

1)How far are you from the intersection when you begin to apply the brakes? I know this answer: 100m.
...i can't figure out the next two. please help me figure out the formula for this!
2)What acceleration will bring you to rest right at the intersection?
3)How long does it take you to stop?
 
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2) You know what distance, [itex]x=+100\ m[/itex], you have to travel to come to a halt, [itex]v=0[/itex], at the traffic light. You also know what velocity you start out with, [itex]v_o=+20\ m/s[/itex], when you apply the brakes at the beginning of the deceleration.
 
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