the runner runs at top speed for 7.9 seconds, so
1/2 a*2.1^2 + 2.1a*7.9 = 100
a=5.32
v = at = 5.32*2.1 = 11.172 m/s
check:
accelerating at 5.32m/s^2 for 2.1 s gives
s = 1/2 * 5.32 * 2.1^2 = 11.73
From then on with speed = 5.32*2.1 = 11.172, the distance covered is
11.172*7.9 = 88.27
total distance: 100.0 m
A sprinter can accelerate with constant acceleration for 2.10s before reaching top speed. He can run the 100-meter dash in 10 s.
What is his speed as he crosses the finish line?
2 answers
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1 answer