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In Problem 2/54, I have come up with a solution only one decimal place off from the books results. I am posting to see if someone can look over my solution to see if it is correct.

To begin the equation given:

a = u*g - (k/m)x

Only works in cases where it only moves in a direction where the friction force is strictly positive (i.e. the block is moving leftward).

To solve the case of motion in the opposite direction must be considered, the equation for motion opposite this direction is:

a = -u*g - (k/m)x

Now using the relationship in the book:

vdv = ads

Integrating and noting that each starting and stopping point has zero velocity:

(1) 0 = u*g(xf - xi) -(k/2m)(xf^2 - xi^2)

(2) 0 = -u*g(xf - xi) -(k/2m)(xf^2 - xi^2)

Now using (1) the first stop start point occurrs at:

xf = .23866m

On the way back however the motion is reveresed and equation (2) is used to find:

xf = .022666m

The solution in the book was: 23.3mm

Did I make a mistake or why is there such a seemingly slight difference in the answer?


2 Answers 2


I believe my solution is correct based on the solution here: American Physics Journal Solution The phycist uses a different more general method to solve the same problem, following his approach and using his derivations I arrived at the final position being at -22.6mm (in compression). Therefore I will assume the books answer to be a little off from the actual solution. Hope this helps someone later on down the line!

  • $\begingroup$ It doesn't say what value of g is to be used $\endgroup$ Jul 18 at 7:16
  • $\begingroup$ Using g=9.81 and a numerical model I get -22.59 mm $\endgroup$ Jul 20 at 9:52

stackXfriction - simulation of an SDOF system with friction

Despite the title this is not a bouncing ball it is a sliding block final value is -22.59 mm. This is a runge kutta type solution, dt=0.0001 s g=9.81


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