1. Conservation of Energy Energy1 = Energy2 + Friction
Chapter
Conservation of Energy
Energy1 = Energy2 + Friction

2. Objectives Establish a standard energy equation
Establish initial and final conditions
Solve for unknown variable

3. Types of Energy Work Spring Work Potential Energy Kinetic Energy
Friction Work
U = (F) x (s)
SP = (½)kx2
PE = W x h
KE = (½)mv2
Fr = Ff x (s)

4. Conservation of Energy
Energy at condition (1) equals Energy at condition (2) plus friction
KE1+PE1+SP1=KE2+PE2+SP2+Fr
(½)mv12 +Wh1+(½)kx12 =
(½)mv22 +Wh2+(½)kx22 + Ff (x)

5. Example 14 – 10 Conditions: v1=20 ft/s v2 = 0 ft/s
h1 = 0 ft h2 = d(sin 30)
No spring component
Friction = 5 lbs

6. Example 14 – 10 Solution (½)(W/g)v12 +Wh1+(½)kx12 =
(½))(W/g) v22 +Wh2+(½)kx22 + Ff(x)
(Remove factors that equal zero)
(½)(W/g)v12 =Wh2+Ff(x)
(Substitute values)
(.5)(100/32.2)(20)2=(100)(d)(.5)+(5)(d)

7. Example 14 – 10 Answer (.5)(100/32.2)(20)2=(100)(d)(.5)+(5)(d)
d=11.3 ft

8. Angular Kinetic Energy
Rectilinear KE = (½)mv2
Angular KE = (½)I2
Where:
KE in ft-lbs or n-m
I in ft-lb-s2 or kg-m2
 in rad/sec

9. Week 12 Homework
Chapter 14
Problems: 26, 27, 35, 37, 43, 50 & 59 (7th Ed)
Problems: 29, 30, 38, 40, 46, 53 & 62 (8th Ed)
Read Sections thru for next week