Question

A sprinter, running a 100-meter race, can accelerate with a constant acceleration for 4.10 s before reaching his top speed. He can then can maintain that speed for the rest of the race. He runs the 100 meters in 10.0 s. What is the runner's speed as he crosses the finish line?

Answer 1

Answer:

12.579m/s:with constant acceleration the displacement is calculated as follows Δx=(+)t/2for the first 4.10s the  is the top speed so, and, for the other  5.9s, the speed is constant with value ,  so:100 m =*(10-4.1s)+ (0+)4.1s/2so =100/(5.9+2.05)=12.579m/s

Explanation:

Answer 2

Answer:

$v_{f}$=12.579m/s

Explanation:

with constant acceleration the displacement is calculated as follows

Δx=($v_{0}$+$v_{f}$)t/2

for the first 4.10s the $v_{f}$ is the top speed so, and, for the other  5.9s, the speed is constant with value $v_{f}$,  so:

100 m =$v_{f}$*(10-4.1s)+ (0+$v_{f}$)4.1s/2

so $v_{f}$=100/(5.9+2.05)=12.579m/s