Chapter 7. Work and Energy Transfer. Section 7.1- Systems and Environments. System- small portion of the universe being studied Can be a single object Can be a collection of objects Environment- everything outside the boundaries (physical or not) of the system
Work and Energy Transfer
A . B = B . A
A . ( B + C ) = A . B + A . C
Prove this in HW #6
Quick Quiz p. 187
Example 7.2, 7.3
valid when F is constant.
need to look at very
small intervals of Δx
(The smaller the interval, the closer
Fx becomes to a constant value)
Work done on block is positive, the spring force is forward while the block moves forward.
Quick Quiz p 192
Work-Kinetic Energy Theorem
Quick Quiz p 195
Examples 7.7, 7.8
Power is the time rate of change of energy/work
1 kWh = 1000 J/s x 3600 s = 3.6x106 J
~ 67% Lost to heat/sound/emr in the engine
~ 10% Lost in friction of the drivetrain
~ 4 -10% lost to power Fuel Pumps/Alternator/AC
Leaves around 13-19% for Kinetic Energy.