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gizmo_the_mogwai [7]
3 years ago
8

N april 1974, steve prefontaine completed a 10-km race in a time of 27 min, 43.6 s. suppose \"pre\" was at the 7.15-km mark at a

time of 25.0 min. if he accelerates for 60 s and maintains the increased speed for the duration of the race, calculate the acceleration that he had. assume his instantaneous speed at the 7.15-km mark was the same as his overall average speed up to that time.
Physics
1 answer:
aliya0001 [1]3 years ago
6 0

solution:speed is 7.99km ,u=\frac{7990}{(25\times60)}=5.33m/s\\
now let the final velocity after 60s from 7.99km is v.\\
v-u =at\\v=5.33+a\times60\\  =60s+5.33\\now distance travelled during this time will be\\
s_{2}=vt\\
v\times103.6\\
=(60a+5.33)\times103.6\\
=551.84+6216am\\
now total distance travelled  is \\  also\\
s_{1}=ut+(\frac{1}{2})at^{2}      =5.33\times60+(0.5)9\times3600\\
=1800a+319.6m\\
Now the remaining time to complete rest race was\\
t=(27\times60+43.6)60-60(25\times60)\\
=103.6s\\Now, distance travelled during this time will be\\
s_{2}=vt\\
v\times103.6\\
=(60a+5.33)\times103.6\\
=551.84+6216am\\
now total distance travelled  is \\
s_{1}+s_{2}+7990=10000\\
1800a+319.6+551.84+6216a=2010\\
8016a=2010-871.44\\
8016a=1138.56\\
a=0.142m/s^2

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