2b the same box is pushed by a 20 nm spring as it

Info icon This preview shows pages 14–15. Sign up to view the full content.

2b. The same box is pushed by a 2.0 N/m spring as it relaxes, from x=-5.0cm to x=0.0 cm. What is the work done by the spring? W = - 1 2 (2 . 0)((0) 2 - ( - 5 . 0) 2 ) J = +25 J You can ’t fail to notice that in both examples the work for the round trip vanishes.
Image of page 14

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Phys 2A - Mechanics 3a. The same box is pushed on a rough surface with coefficient of kinetic friction 0.7 from the origin to the point x=1.0m. Determine the work done by the force of friction. The examples above must seem vaguely familiar, they look a lot like the computation of potential. Here is something new: W = Z x f x i F friction ,x dx = Z x f x i ( - μ k mg ) dx = - μ k mg ( x f - x i ) W = - (0 . 7)(20)(9 . 8)(1 . 0 - 0) J = - 140 J 3b. The same box is pushed on a rough surface with coefficient of kinetic friction 0.7 from the point x=1.0m to the origin. Determine the work done by the force of friction. W = Z x f x i F friction ,x dx = Z x f x i (+ μ k mg ) dx = + μ k mg ( x f - x i ) W = +(0 . 7)(20)(9 . 8)(0 - 1 . 0) J = - 140 J Wow! The work done on the round trip does not vanish! Motion to the right Force points left: negative Motion to the left Force points right: positive
Image of page 15
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern