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Friction Problem Solving


Directions:  The following problems are found in your Physics text in Chapter 5, pages 114- 118.  Use the teacher’s notes written for this chapter, and read examples 5-6, 5-7, 5-8, 5-9, 5-10, 5-11, 5-12, 5-13, and 5-15.

      Solutions to the following problems are found on linked pages.  Try to solve a given problem before resorting to the guided solution.

5-1, 5-2, 5-3, 5-4, 5-5, 5-7, 5-8(b), 5-20, 5-21, 5-24 (Word doc.), 5-29 (Word doc.), 5-33 (Word doc.), 5-36 (Word doc.). 

Also, these additional problems:

      Sample Friction Problem:  The Inclined Plank (Word) (Adobe Acrobat.pdf: page 1, page 2, page 3, page 4, page 5).  Pages 3, 4, 5 will be published soon.  A math error just discovered requires re-writing of these pages.

Sample Friction Problem:  The Skier (Word) (Adobe Acrobat.pdf: page 1, page 2)

    To access hand-written "Teacher's Notes", which have been saved in ".pdf" format, click on:    for a free download of Adobe Reader.


(1)  A 500 Nt crate is pushed from behind along a flat and level floor, where μK = 0.48.  The person's effort of 639 Nt is oriented at 39 above the horizontal.  If the crate begins at rest and reaches a final speed of 3 m/sec,

    (a)  what is the crate's acceleration?

    (b)  over what distance is the crate pushed?

    (c)  what is the elapsed time?


(2)  A 50-lb box of machine parts is placed on an inclined plank 5 ft in length, where the elevated end is placed at the opening of a loading deck 3 ft above the ground.  If μK = 0.60, determine the behavior of the box:

    (a)  will it remain stationary or will it immediately begin to accelerate down the plank?

    (b)  if the box accelerates, what is the magnitude of its acceleration?

    (c)  if the box tends to move, with what restraining force (FE) must a worker push parallel to the plank against the front of the box to prevent it from sliding?

    (d) what will be the velocity of the box at the bottom of the plank?

    (e)  how long will it take the box to reach the bottom of the plank?