Afootball player carrying the ball runs straight ahead at the line of scrimmage and directly into a wall of defensive linemen. the ball carrier has an initial speed of 7.68 m/s and is stopped in a time interval of 0.202 s. find the magnitude and direction of his average acceleration.

For this problem, we use the derived equations for rectilinear motion at constant acceleration. The equation is:

a = (v -v₀)/t
where
v and v₀ is the final and initial velocities, respectively
t is time
a is acceleration

Since it eventually comes to a stop, v=0. Substituting the values,
a = (0 - 7.68 m/s)/0.202 s
a = -38.02 m/s²

Hence, the magnitude of the acceleration is -38.02 m/s². The direction is still aiming along the straight line, but the negative sign signifies that the the ball is decelerating.