Calculating Acceleration, Displacement for 100m Sprint

[Veronica_Oles]

Homework Statement

In a 100 m sprint a runner starts from rest and accelerate to 9.6 m/s [W] in 4.2 s.
Calculate acceleration, displacement, and if the runner runs at a constant velocity for the rest of the race what is the total time?

Homework Equations

The Attempt at a Solution

I am having trouble with the total time. I know acceleration is 2.3 m/s^2 [W] and I know displacement is 20.16 m [W]. However what would the constant velocity be.. Is it 9.6 m/s[w]? And since it states the rest of the race does that mean i have to subtract 20.16 from the 100m?

 

[Veronica_Oles]

Homework Statement

In a 100 m sprint a runner starts from rest and accelerate to 9.6 m/s [W] in 4.2 s.
Calculate acceleration, displacement, and if the runner runs at a constant velocity for the rest of the race what is the total time?

Homework Equations

The Attempt at a Solution

I am having trouble with the total time. I know acceleration is 2.3 m/s^2 [W] and I know displacement is 20.16 m [W]. However what would the constant velocity be.. Is it 9.6 m/s[w]? And since it states the rest of the race does that mean i have to subtract 20.16 from the 100m?

So what I did was take 100 subtract 20 to obtain 80. Then I took 80 divided it by 9.6 took that number and added 4.2 seconds to get the total time. The total time is 13s.. Can someone tell me if I did this correctly?

 

[haruspex]

So what I did was take 100 subtract 20 to obtain 80. Then I took 80 divided it by 9.6 took that number and added 4.2 seconds to get the total time. The total time is 13s.. Can someone tell me if I did this correctly?

Looks good.