9. 40%) (a) A sprinter starting from rest ve o m/s)on a straight evel track babl

Question

9. 40%) (a) A sprinter starting from rest ve o m/s)on a straight evel track bable to achieve a speed of 15 m/s in a time of e s. What is the and acceleration? rinter's average (b) What will be her speed if she continues this acceleration for another 10 seconds? 10. (40%) A sprinter starting from rest on a straight and level track is able to travel a distance of 100.0 m in a time of 10.0 s. a) What is the sprinter's average speed? (Show your calculations.) bo what is the sprinter's average in mileshour? (Show your calculations) 11. 40%) A ball is dropped from the top of an 80.0 m building. (a) Neglecting air resistance, how long does it take to reach the ground. (b) What speed is it traveling the instant before it hits the ground?

Explanation / Answer

(9):

avg acceleration = (total chang ein velocity ) / (total time taken ) = (15-0) / 3 = 5 m /s^2

(10):

(a):

avg. speed = (total istance covered) / (total time taken) = (100) / (10) = 10 m/s

(b):

avg speed = 10 * (3600/1000*1.61) = 22.36 miles/hour

(11):

initial speed of ball = 0 m/s

acceleration of ball is = g = 9.8 m/s^2

s = ut + (1/2)*a*t^2

80 = 0 + (1/2)*9.8*t^2

t= 4.0406 s. ..........answer (a)

(b):

v = u + at

v = 0 + 9.8*4.0406

v = 39.5979 m/s

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