Acceleration question (should be easy?)

[David Donald]

Homework Statement

A person runs in front of you. The person accelerates uniformly from 4.0 m/s to 8.0 m/s in a time of 4.0 s.
What is the magnitude of the acceleration of the person during the 4.0 s?

Homework Equations

Kinematics

The Attempt at a Solution

Vfx = Vox + at
(Vfx - Vox)/t = a

so (8m/s - 4m/s)/(4s) = a = 1.0 m/s^2

this is wrong though, so what am i failing to understand here?

 

[andrewkirk]

It looks right to me. Does the book give a reason for its answer? Perhaps the book's answer is wrong - they sometimes are.

 

[David Donald]

apparently it should be 0.8 m/s^2 ?

 

[andrewkirk]

Check the problem statement. Perhaps the time was 5s, not 4.