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## Homework Statement

You are passing a construction site on the way to physics class, and stop to watch for a while. The construction workers appear to be going on a coffee break, and have left a large concrete block resting at the top of a wooden ramp connecting one of the building's upper floors to the ground. As soon as their backs are turned, the block begins to slide and takes about 2 seconds to reach the ground. You wonder how long the ramp is. You estimate the ramp is at an angle of about 37* to the horizontal, and your physics book gives the coefficient of kinetic friction (uk) between concrete and wood as 0.25

## Homework Equations

a= F/m

vf=vi+at

vf^2=vi^2+2ax

## The Attempt at a Solution

I found that:

Fnety = Fn - Fgy = Fn - mgsin(37) = 0

Fn = mgsin(37)

Fnetx = Ff - Fgx = uk(mg)sin(37) - mgcos(37) = ma

a = uk(g)sin(37) - gcos(37)

a = .25(-9.8)sin(37) + 9.8cos(37)

a = 6.35 m/s^2

vf-vi = at

vf = 6.35(2)

vf = 12.7 m/s

vf^2 - vi^2 = 2ax

12.7^2 = 2(6.35)x

x = 12.7m

I don't understand how this is wrong?