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Mario drives up with a constant speed of 18,0 m s-1 in a kart. At the point in time (t) t = 0 seconds he sees a barrel further on the racetrack. After 0,45 he jams on the brakes. This is the point of time belonging to R. There are 20 pictures per second. 

 

 

a. Explain which point (A, B or C) belongs to t = 0 seconds.

b. Mario brakes as hard as possible, but still collides at t = 3 seconds with a speed of 2,4 m s-1 with the barrel. Assume he immediately comes to a still and stays still till t = 4 seconds. Calculate the distance the car covers from t = 0 seconds.

 Jan 10, 2020
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Pt A is t = 0      there are 9 pictures (red dots) to where he is now

     9 pictures / 20 pictures/s = .45 s

 

He is going 18 m/s from t = 0 to t = .45 s         distance = .45 x 18 = 8.1 m

 

  Then he begins deccelerating to 2.4 m/s  from .45 to t = 3 sec 

        then he instantly stops (I do not know why they tell you he stays still until t = 4 sec)

 

vf = v0  + a t             t is 3 - .45 = 2.55s

2.4 = 18+ a (2.55)

    results in a = - 6.18  m/s^2

 

how far did he travel while braking (which we will add to the 8.1 m above)

    xf = x0 + vo t + 1/2 a t^2 

    xf =         18 (2.55) + 1/2 (-6.18) (2.55^2)

        =     26.01 m

 

Add the 8.1      distance = 34.11 m

 Jan 10, 2020

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