Final-solutions 1 - PHYSICS 221 FINAL EXAM Section 1...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
PHYSICS 221 FINAL EXAM Section 1, December 2010 SOLUTIONS Problem 1: [12pt] A football player kicks a ball with a speed of 22.0 m/s at an angle of 49.0 o above the horizontal, a distance of 39.0 m from the goal post. (a) [6pt] What is the height of the ball above the ground when it reaches the goal post? The horizontal and vertical position are given by with m/s, m/s. Then 39 m/(14.4 m/s) 2.71 s, and (b) [6pt] What is the ball’s vertical velocity when it reaches the goal post? Give a positive velocity upward, negative downward.
Image of page 1

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

View Full Document Right Arrow Icon
2 Problem 2: [12pt] A uniform ladder has a length of m and it leans against a frictionless wall at an angle of , as shown. The ladder weighs 34.0 lb, and a 90.0 lb boy climbs a distance m up the ladder. (a) [6pt] Find the magnitude of the frictional force in pounds. (There is no need to convert units.) Let and denote the weight of the ladder and boy. Balancing torques about the bottom of the ladder gives Balancing forces in the horizontal direction gives Therefore, (b) [6pt] If the floor is slippery and has coefficient of friction with the ladder, what is the greatest distance the boy can climb before the ladder slips? The same equations apply as in part (a), together with and the vertical equilibrium condition Then (0.250) (124 lb) = 31.0 lb. Now is unknown, and satisfies
Image of page 2
3 Problem 3: [12pt] A ball of mass kg is dropped from a height m above a large spring with spring constant 600 N/m. (a) [6pt] What is the total work done on the ball during the spring’s compression , from the time it contacts the spring to the time it momentarily comes to rest? Include the correct sign. The work done on the ball is its change in kinetic energy, By energy conservation, the kinetic energy of the ball at the top of the spring is Therefore, (b) [6pt] Find the maximum compression distance of the spring before it rebounds.
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
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