A child on a skateboard is traveling at a velocity of 8 m/s down a hill. At the bottom of the hill, he slows down and comes to a stop in 4 seconds. Calculate the sled's deceleration. Depict which equation to use

a=vf-vi/t
t=vf-vi/a
vf=(a•t)+vi

Use the profile illustrated for problem (1). assume that the layer of silty sand fill (sm) is placed over the entire site. estimate the thickness of the fill (h - in feet) that will cause the effective vertical stress at the center of the clay layer to increase by 517.5 pounds per square foot.