Physics

posted by .

100 m from a traffic light, a motorist sees it to red. If he needs to accelerate at -1 m.s ^2 to stop at the traffic light, what is the initial speed, and how long did he take to stop?

  • Physics -

    Let initial speed = Vo
    Average speed while decelerating = Vo/2
    X = 100 m
    Time to decelerate to zero =
    T = 2 X/Vo
    also,
    T = Vo/a.
    Therefore
    2X/Vo = Vo/a
    Vo = sqrt(2 a X) = 14.1 m/s
    T = 14.1/1 = 14.1 s

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Physics

    You are sitting in your car at a traffic light at the foot of a 200 ft long ramp that will take you onto the interstate. If your cat can at best accelerate at 5 m/s^2 and the traffic on the interstate is moving at 65mph. will the ramp …
  2. Physics

    A car is going 20m/s when they see a traffic light 200m ahead turn red. The traffic light is known to stay red for 15s. The driver wants to reach the light as it turns green. It takes them 1s to press the breaks and the car slows down …
  3. physical Science

    The Mass Of A Minibus with The Driver is 1500 kg.the Driver Is Moving At A Speed Of 30 m.s When He Notices That The traffic light Ahead Have turned To red.he Applies A Force Of 9000N on the brake pedal. A)calculate his deceleration …
  4. physics

    Consider a horizontal road with such a set of traffic lights, each spaced 100 m apart. A car sits at the first traffic light. At t=0 the light turns green and the car accelerates. What is the maximum time t in secondsthe next …
  5. science

    When the front of a 5.0 m long bus traveling at a constant speed of 20 m/s is 55 m away from an intersection, the traffic light turns yellow. It will take 3.0 s before the traffic light turns red. The driver’s reaction time is 0.25 …
  6. phys

    A motorist is driving at 20m/s{\rm m/s} when she sees that a traffic light 200m{\rm m} ahead has just turned red. She knows that this light stays red for 15s{\rm s} , and she wants to reach the light just as it turns green again. It …
  7. physics

    A motorist is driving at 20m/s{\rm m/s} when she sees that a traffic light 200m{\rm m} ahead has just turned red. She knows that this light stays red for 15s{\rm s} , and she wants to reach the light just as it turns green again. It …
  8. physics

    The car stationary in front of a red traffic light. As the light turns green , a truck goes past at a constant velocity of 1.5 m/s. At the same moment , the car begins to accelerate at 1.25 m/s 2 . When it reaches 2.5 m/s the car continues …
  9. physics

    The car stationary in front of a red traffic light. As the light turns green , a truck goes past at a constant velocity of 1.5 m/s. At the same moment , the car begins to accelerate at 1.25 m/s 2 . When it reaches 2.5 m/s the car continues …
  10. applied mechanics

    a motorist driving his car at a speed of 72km/hr observes that the traffic lights ahead of him turns red if he comes to a halt at the traffic light 5seconds starting from first find the distance of the car from the light when the motorist …

More Similar Questions