1 / 9

Chapter 7

Chapter 7. Work and Kinetic Energy (Continued). Outline. Kinetic energy Work-energy theorem Power Examples. Kinetic Energy. Kinetic energy K: The energy of motion. K = (1/2)mv 2 , where v is the speed. SI units for kinetic energy: joule (J).

samson
Download Presentation

Chapter 7

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. Chapter 7 Work and Kinetic Energy (Continued) Dr. Jie Zou PHY 1151G Department of Physics

  2. Outline • Kinetic energy • Work-energy theorem • Power • Examples Dr. Jie Zou PHY 1151G Department of Physics

  3. Kinetic Energy • Kinetic energy K: The energy of motion. • K = (1/2)mv2, where v is the speed. • SI units for kinetic energy: joule (J). • Kinetic energy is always greater than or equal to zero. • Example: Consider your kinetic energy when jogging. Assuming a mass of about 62 kg and a speed of 2.5 m/s, your kinetic energy is K = (1/2)mv2 = (1/2)(62 kg)(2.5 m/s)2 = 190 J. Dr. Jie Zou PHY 1151G Department of Physics

  4. Work-Energy Theorem • Work-energy theorem: The total (net) work done on an object is equal to the change in its kinetic energy. • Wtotal = K = (1/2)mvf2 - (1/2)mvi2 • Here vf and vi are the final and initial speed of the object, respectively. Dr. Jie Zou PHY 1151G Department of Physics

  5. Example 7-5 • A 4.1-kg box of books is lifted vertically from rest a distance of 1.6 m by an upward applied force of 60.0 N. Find • (a) The work done by the applied force. • (b) The work done by the force of gravity. • (c) Use work-energy theorem and find the final speed of the box. • Can you use kinematics equations to solve (c)? Dr. Jie Zou PHY 1151G Department of Physics

  6. Example 2 • A boy exerts a force of 11.0 N at 29.0 above the horizontal on a 6.40-kg sled. Find the work done by the boy and the final speed of the sled after it moves 2.00 m, assuming the sled starts with an initial speed of 0.500 m/s and slides horizontally without friction. Dr. Jie Zou PHY 1151G Department of Physics

  7. Power • Power: A measure of how quickly work is done. • Average power = W / t. • W is the work done in time t. • SI units: J/s = watt (W). • 1 horsepower (hp) = 746 W. Dr. Jie Zou PHY 1151G Department of Physics

  8. Example 7-8 • To pass a slow-moving truck, you want your 1.30103 kg-car to accelerate from 13.4 m/s (30.0 mph) to 17.9 m/s (40.0 mph) in 3.00 s. What is the minimum power required for this pass? Dr. Jie Zou PHY 1151G Department of Physics

  9. Homework • See online homework assignment at www.masteringphysics.com Dr. Jie Zou PHY 1151G Department of Physics

More Related