Energy Chapter 11 Chapter 11: Energy 1/1/2019
Kinetic Energy and Work KE = 0 W = F·d KE = W KE = ½mv2 Chapter 11: Energy 1/1/2019
Example A baseball having a mass of 0.2kg is thrown by a pitcher. The pitcher applies a force of 75N on the ball for a distance of 2m. How fast will the ball be traveling when it leaves the pitcher’s hand? Chapter 11: Energy 1/1/2019
½mv2 = F·d m Given: m= 0.2kg F = 75N d = 2m Equation: K = W v = 2F·d Example Given: m= 0.2kg F = 75N d = 2m Equation: K = W ½mv2 = F·d v = 2F·d m Chapter 11: Energy 1/1/2019
(0.2kg) v = 2(75N)(2m) v = 39 m/s (88mph) Example Chapter 11: Energy 1/1/2019
Stored Energy: Potential Energy(PE) Gravitational (PEg) Chapter 11: Energy 1/1/2019
Gravitational Potential Energy PE = F · d m Ug = (m·g)·h h Chapter 11: Energy 1/1/2019
You lift a 2kg textbook from the floor to a shelf 2m above the floor. Example You lift a 2kg textbook from the floor to a shelf 2m above the floor. 1. What is the books Ug relative to the floor? 2. What is the books Ug relative to the top of your head if you are 1.5 m tall? Chapter 11: Energy 1/1/2019
Example 2m 1.5m Chapter 11: Energy 1/1/2019
Given: m= 2kg hs = 2m hh = 1.5m Equation:Ug = m·g·h Example Given: m= 2kg hs = 2m hh = 1.5m With respect to the floor. Equation:Ug = m·g·h Ug = (2kg)(9.8m/s2)(2m) Ug = 39.2 J Chapter 11: Energy 1/1/2019
Equation:Ug = m·g·h Ug = (2kg)(9.8m/s2)(2m-1.5m) Ug = 9.8 J Example With respect to the top of your head. Equation:Ug = m·g·h Ug = (2kg)(9.8m/s2)(2m-1.5m) Ug = 9.8 J Chapter 11: Energy 1/1/2019
Problems: 1-4 Page:251 Problems: 5-8 Page:254-255 Due: 2/11/03 Homework: 11-1 Problems: 1-4 Page:251 Problems: 5-8 Page:254-255 Due: 2/11/03 Chapter 11: Energy 1/1/2019
Conservation of Energy Total energy of a system remains unchanged!! E = PE + KE Chapter 11: Energy 1/1/2019
Energy Conversion Chapter 11: Energy 1/1/2019
Chapter 11: Energy 1/1/2019
Energy in a falling object. E =KE + PE Ug = mgh h = 16m K = ½mv² h = 12m v = 2gd h = 8m h = 4m Chapter 11: Energy 1/1/2019
16 157 12 9 118 39 8 13 78 79 4 15 18 height h (m) Speed v= 2gd (m/s) Potential Ug=mgh (J) Kinetic K=½mv² Total E=Ug+K 16 157 12 9 118 39 8 13 78 79 4 15 18 Chapter 11: Energy 1/1/2019
Analyzing Collisions v1a=.2m/s v1a=1.2m/s m2=1kg v2b=0m/s m1=1kg Chapter 11: Energy 1/1/2019
1 1 1 1 0.5 0.5 0.5 0.25 p=mv K=½mv² Before (J) Case I After Case II Case III p=mv K=½mv² 1 1 1 1 0.5 0.5 0.5 0.25 Chapter 11: Energy 1/1/2019
Problems: 9-12 Page:261-262 Due: 2/12/03 Homework: 11-2 Chapter 11: Energy 1/1/2019
Problems: 13-16 Page:265 Due: 2/25/03 Homework: 11-2 Chapter 11: Energy 1/1/2019
Problems: 36, 37, 39, 42, 46, 49 and 56 Pages:269-270 Due: 2/13/03 Homework: 11-3 Problems: 36, 37, 39, 42, 46, 49 and 56 Pages:269-270 Due: 2/13/03 Chapter 11: Energy 1/1/2019
Problems: 52, 53, 57, 58 and 62 Pages: 270-271 Due: 2/14/03 Homework: 11-4 Problems: 52, 53, 57, 58 and 62 Pages: 270-271 Due: 2/14/03 Chapter 11: Energy 1/1/2019