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Maurice Greene once ran the 100-m dash in 9.81 s (the wind was at his back), and Khalid Khannouchi ran the marathon (26 mi, 385 yd) in 2:05:42. (a) What are their average speeds? (b) If Maurice Greene could maintain his sprint speed during a marathon, how long would it take him to finish?

Maurice Greene once ran the 100-m dash in 9.81 s (the wind was at his back), and Khalid Khannouchi ran the marathon (26 mi, 385 yd) in 2:05:42. (a) What are their average speeds?             
(b) If Maurice Greene could maintain his sprint speed during a marathon, how long would it take him to finish?

Grade:11

1 Answers

Aditi Chauhan
askIITians Faculty 396 Points
9 years ago
(a)
Substitute 100m for “distance” and 9.81s for “elapsed time” in equation average\ speed = \frac{distance}{elapsed\ time} to calculate the average speed of Maurice Greene as,
average\ speed = \frac{100 m}{93.81 s}
= 10.2 m/s

Therefore, the average speed of Maurice Greene is . 10.2 m/s.
Substitute 26 mi for “distance” and 2 g 5 min 42 sec for “elapsed time” in equationaverage\ speed = \frac{distance}{elapsed\ time} to calculate the average speed of Khalid Khannouchi as,

236-2248_khurak.JPG
Therefore, the average speed of Khalid Khannouchi is 5.54 m/s.
(b)

Substitute 26 mi for “distance” and 10.2 m/s for “average speed” in equation elapsed time = \frac{distance}{ average\ speed}, to calculate the elapsed time of Maurice Greene as:

236-1129_should.JPG
Therefore, Maurice Greene can finish the marathon in. 1.13 h.

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