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Homework Help: Question relates to Degree and some other simple question.

  1. May 7, 2012 #1
    1. Marcia was driving her car at the constant speed of 19.2 m/s when she saw the light turn red. It took her .13 sec to hit the brakes, but then the car slowed at the constant rate of 6.2 m/s2 until it stopped. How much time did it take for the car to stop moving after the light turned red.? How far did the car travel until it stopped?
    Did I plug in the right number for each symbol?

    I am confuse of which equation to use and which question should I put .13s to.

    First question:

    V0 = 19.2 m/s
    A = -6.2 m/s 2
    Δt = ?


    Δx = V0Δt + .5a(Δt)2

    Second question:
    V0 = 19.2 m/s
    A = -6.2 m/s 2
    Δt = .13 s


    Δx = V0Δt + .5a(Δt)2

    2. Standing on a flat roof of a 21 m high building, Ali threw a ball up at a 60 degree angle to the roof top. The speed of the ball was 25 m/s. When the ball left Ali’s outstretched hand the ball was 3.1 meters from the roof top. The ball eventually landed on the roof. High far was the ball from Ali?

    I never work on question related to degree, so I am pretty lost on this one.
    Vo = 25m/s
    A = -9.8 m/s 2
    Vf = 0 m/s
    Δx = ?

    3. Maxim was driving his car at 15 m/s when he pressed the gas pedal down to accelerate at 5.2 m/s2. How far did he travel in the next 2.5 seconds?

    I think this is correct.
    Δx = ?
    V0 = 15 m/s
    Δt = 2.5 s
    A = -5.2 m/s 2

    Δx = V0Δt + .5a(Δt)2

    Δx = 15 m/s (2.5 s) – 5.2 m/s 2 (2.5 s 2)

    Δx = 37.5 m – 32.5 m

    Δx = 5m
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 8, 2012 #2
  4. May 9, 2012 #3
    1. Draw a velocity - time graph.
    2. Not sure how the rooftop and roof configuration.
    3. Why the acceleration is negative? Draw a velocity- time graph here too.
    Last edited: May 9, 2012
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