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Homework Help: The speed of a car with constant acceleration

  1. Sep 15, 2011 #1
    1. The problem statement, all variables and given/known data
    A sports car accelerates in third gear from 48.3 km/h to 80.5 hm/h in 3.7 seconds. (a)What is the average acceleration of this car in m/s^2? (b) If the car maintained this acceleration, how fast would it be moving one second later?

    2. Relevant equations

    a= dv/dt
    1km = 1000 m
    1 h = 60s

    3. The attempt at a solution
    (a) I did 48.3 km/h to 805 m/s and 80.5 km/h to 4025/3 m/s; plugged them into the a formula-> (4025-(805)3)/3 which gives you (1610/3)/3.7 (since 3.7 is delta t), and my final answer 145 m/s^2.

    (b) This is the part I'm having trouble with, do I just use 4.7 instead of 3.7 for t?
  2. jcsd
  3. Sep 15, 2011 #2


    User Avatar

    Staff: Mentor

    1 h is not 60s. 1 minute is 60s.

    For part (a) you should check your conversions from km/hr to m/s. Can you show your work?

    For part (b) you should state a kinematic formula that is applicable, and yes, you'd then use 4.7s in that formula (along with the acceleration that you calculate in part (a)).
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