Unit 3 Work, Energy & Power Serway Chapters 7 & 8 1 Unit 3 Section 2 Energy and the Work-Energy Theorem

Unit 3 Section 2 Lesson 1 Kinetic Energy and the Work-Energy Theorem Unit 3 Section 2 Lesson 1 Kinetic Energy Objectives: ▫Show understanding of the Physics concept of Kinetic Energy ▫Correctly identify Kinetic Energy from given situations ▫Recall and show understanding of the formula to calculate Kinetic Energy ▫Solve related problems involving Change in Kinetic Energy ▫KE = ½ mv 2 ▫Work = ΔKE = (½ mv 2 ) final – (½ mv 2 ) initial ▫Do NOW: Charles is vacuuming room 3. He pushes the vacuum with a 5.00 N force at an angle of 30.0 degrees to the horizontal. If he pushes the vacuum 3.00 meters across the carpet, what is the work he did? ▫Unit 3 Section 2 Lesson 1 HOMEWORK: DUE MON Jan 14 ▫Serway PAGE:209 : #’s 27, 30, 31, 33, 34, 37, 40, 41 2

Energy – Energy is the capacity to do WORK SI Unit: Joule (J) Many forms Common ones: ▫Kinetic ▫Potential ▫Electric ▫Chemical ▫Solar ▫Nuclear 3

Kinetic Energy KE = ½ (mv 2 ) A form of energy that a body in motion possess. Examples: ▫ Bullet shot out from pistol ▫ Helicopter flying at 120km/h A body a rest, will NOT possess any KE! The amount of KE of a moving body depends on: ▫ Mass of body (kg) ▫ Velocity (m/s) When either mass or velocity of moving body is increased, KE will also increase. Kinetic Energy = ½ (Mass)(Velocity) 2 = ½ (mv 2 )  [ J ] = [kg] [m/s] 2 Mass Doubles Kinetic Energy Doubles Velocity Doubles Kinetic Energy QUADRUPLES 4 Mass = m Velocity, V

DO NOW: Examples of KE Find the KE of an empty van of mass 1000kg moving at 2m/s. Find the KE of van when it is loaded with goods to give a total mass of 2000kg, and moving at 2m/s. Find KE of unloaded van when it speeds up to 4m/s. 5 KE of van at 2m/s = ½ x 1000 x (2) 2 = 2000 J = 2 kJ KE of van at 2m/s = ½ x 2000 x (2) 2 = 4000 J = 4 kJ KE of van at 2m/s = ½ x 1000 x (4) 2 = 8000 J = 8 kJ

Work – Kinetic Energy Theorem Serway page 195 W = ∫ F dx  ∫ ma x dx Work = ΔKE = (½ mv 2 ) final – (½ mv 2 ) initial If you push a 6.0 Kg object from rest along a frictionless surface with a force of 12.0 N what will the velocity be after 3 meters? Romac loads a refrigerator for Claire onto his truck using a frictionless ramp. He claims that less work is required to load the truck if the ramp is lengthened. Is he correct? Serway page 196 Exp 7.7 – CY:3.5 AL: 3.6 CC: 3.4 EW: 2.8 PP:0.0 DH: 3.1