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I am stuck on a problem from the 5 Steps to a 5: AP Physics B&C book and would really appreciate anyone's help.

Determine (a) the acceleration of the block down the plane and (b) the time for the block to slide to the bottom of the plane.

http://02.edu-cdn.com/files/static/mcgrawhillprof/9780071623209/INCLINED_PLANES_08.GIF [Broken]

F=ma

F, gravity = mg

F, friction = umg

Kinematic equation ???

Fx, up the plane = mgsin25 + umgcos25 = 204 N

a = F/m = 204/30 = 6.8 m/s^2

Fx, down the plane = mgsin25 - umgcos25 = 44 N

a = F/m = 44/30 = 1.5 m/s^2

I tried using x = Vot + 1/2 at^2 (x = 20 m, Vo = 3m/s) and v = Vo + at (v = 0, Vo = 3 m/s) to solve for time, but my answers were way off on both attempts.

## Homework Statement

Determine (a) the acceleration of the block down the plane and (b) the time for the block to slide to the bottom of the plane.

http://02.edu-cdn.com/files/static/mcgrawhillprof/9780071623209/INCLINED_PLANES_08.GIF [Broken]

## Homework Equations

F=ma

F, gravity = mg

F, friction = umg

Kinematic equation ???

## The Attempt at a Solution

Fx, up the plane = mgsin25 + umgcos25 = 204 N

a = F/m = 204/30 = 6.8 m/s^2

Fx, down the plane = mgsin25 - umgcos25 = 44 N

a = F/m = 44/30 = 1.5 m/s^2

I tried using x = Vot + 1/2 at^2 (x = 20 m, Vo = 3m/s) and v = Vo + at (v = 0, Vo = 3 m/s) to solve for time, but my answers were way off on both attempts.

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