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Posted by rangjavi 3 years ago In:

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rangjavi
rangjavi Asked:

Physics problem

John and Mike were runing a race. john is a faster runner so he gives Mike a head start of 4 meters before he starts the race. Mikes initial velocity is .25 m/s and accelerates at .3 m/s^2. john leaves the gate at 1 m/s and accelerates at 4.2 m/s^2. At which point do they cross paths?

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Answers

OronD
OronD Answered:

Hi,
S = Vo*t + 0.5 * a * t^2
Mike:   O.25t + 0.5 * 3 * t^2
John:   1t + 0.5 * 4.2 * t^2
We have to add 4 meters so that the distances will be equal:
4 + O.25t + 0.5 * 0.3 * t^2 = 1t + 0.5 * 4.2 * t^2
4 + 0.25t + 0.15t^2 = 1t + 2.1t^2
1.95t^2 + O.75t -4 = 0
195t^2 + 75t - 400 = 0
37t^2 + 15t - 80 = 0 
Sorry have to leave now: get the t and from here get the distance.
Best regards,


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