When Jim and Rob ride bicycles, Jim can only accelerate at three-quarters the acceleration of Rob. Both startfrom rest at the bottom of a lo

Question

When Jim and Rob ride bicycles, Jim can only accelerate at three-quarters the acceleration of Rob. Both startfrom rest at the bottom of a long, straight road with constant upward slope. If Rob takes 5.0 minutes to reach thetop, how much earlier should Jim start in order to reach the top at the same time as Rob

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Vân Khánh 5 months 2021-08-22T00:48:02+00:00 1 Answers 61 views 0

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    2021-08-22T00:49:29+00:00

    Answer:

    46.4 s

    Explanation:

    5 minutes = 60 * 5 = 300 seconds

    Let g = 9.8 m/s2. And \theta be the slope of the road, s be the distance of the road, a be the acceleration generated by Rob, 3a/4 is the acceleration generated by Jim .  Both of their motions are subjected to parallel component of the gravitational acceleration gsin\theta

    Rob equation of motion can be modeled as s = a_Rt_R^2/2 = a300^2/2 = 45000a[/tex]

    Jim equation of motion is s = a_Jt_J^2/2 = (3a/4)t_J^2/2 = 3at_J^2/8

    As both of them cover the same distance

     45000a = 3at_J^2/8

    t_J^2 = 45000*8/3 = 120000

    t_J = \sqrt{120000} = 346.4 s

    So Jim should start 346.4 – 300 = 46.4 seconds earlier than Rob in other to reach the end at the same time

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