Question about constant acceleration

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To solve the problem of stopping at a red light from a speed of 20 m/s with a reaction time of 0.5 seconds, the initial distance from the intersection when braking starts is confirmed as 100 m. To find the required acceleration to stop exactly at the intersection, the formula derived from kinematic equations can be applied, using the initial velocity and final velocity (0 m/s). The time taken to stop can also be calculated using the same kinematic principles, factoring in the distance and initial velocity. The key equations involve the relationship between distance, velocity, acceleration, and time. Understanding these formulas will lead to accurate calculations for both acceleration and stopping time.
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, x=+100\ m, you have to travel to come to a halt, v=0, at the traffic light. You also know what velocity you start out with, v_o=+20\ m/s, when you apply the brakes at the beginning of the deceleration.
 
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