1 / 13

Energy Conservation

Energy Conservation. And Non-Conservative Forces. Conservation of Mechanical Energy. Definition of mechanical energy:. (8-6). Using this definition and considering only conservative forces, we find. Or equivalently. Conservation of Mechanical Energy.

ember
Download Presentation

Energy Conservation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Energy Conservation And Non-Conservative Forces

  2. Conservation of Mechanical Energy Definition of mechanical energy: (8-6) Using this definition and considering only conservative forces, we find Or equivalently

  3. Conservation of Mechanical Energy Energy conservation can make kinematics problems much easier to solve

  4. Catching a Home Run At the bottom of the 9th inning,a player hits a 0.15 kg baseball overthe outfield fence. The ball leaves the bat with a speed of 36.0 m/sand a fan in the bleachers catchesit 7.2 m above the point where itwas hit. Neglect air resistance. (a) What is the kinetic energy Kf of the ball when caught? (b) What is the speed vf of the ball when caught.

  5. Speed and Path Energy is a scalar. The speed of the cap is vi at height yi and its speed is vf at height yf, independent of the path between the two heights. Thus the angle at which the cap is launched does not change this result, as long as vi is large enough to carry the cap to height yf.

  6. m 2m h Energy of a Ball ACT When a ball of mass m is dropped from height h, its kinetic energy just before landing is K. If a 2nd ball of mass 2m is dropped from height h/2, what is its kinetic energy just before landing? (a) K/4 (b) K/2 (c) K (d) 2K (e) 4K

  7. Non-conservative Forces In the presence of non-conservative forces, the work done by these forces must be included in the energy calculations. This term is equal to the energy expended in overcoming the non-conservative force (usually friction) or to the energy gained from work done by the non-conservative force. Enc = -Wnc

  8. Galileo’s Pendulum ACT How high will the pendulum swing on the other side now? A) h1 > h2 B) h1 = h2 C) h1 < h2 Conservation of Energy (Wnc=0) Kinitial + Uinitial = Kfinal+Ufinal 0 + mgh1 = 0 + mgh2 h1 = h2 m h1 h2 44

  9. Find the Diver’s Depth A 95.0 kg diver steps off a diving board and drops into the water, 3.00 m below. At some depth d below the water’s surface, the diver comes to rest. If the non-conservative work done on the diver is Wnc = -5,120 J, what is the depth d? 0 0 of U 0

  10. Judging a Putt 1 A golfer badly misjudges a putt, giving the ball an initial speed v1, which sends the ball a distance d that is only one quarter of the distance to the hole. If the non-conservative force f due to the resistance of the grass is constant, what initial speed v2 would have been needed to putt the ball from its initial position to the hole?

  11. Landing with a Thud A block of mass m1 = 2.40 kg is on a horizontal table with a coefficient of friction mk = 0.450 between them and is connected to a hanging block of mass m2= 1.80 kg as shown. When the blocks are released, they move a distance d = 0.50 m, and then m2 hits the floor. Find the speed of the blocks just before m2 hits.

  12. Potential Energy Curvesand Equipotentials The curve of a hill or a roller coaster is itself essentially a plot of the gravitational potential energy:

  13. Total mechanical energy Potential Energy Curves The potential energy curve for a mass and spring

More Related