1. How is Work and Power Related? Chapter 5 Work and Power
Goals: define and calculate work, energy, kinetic energy, potential energy, power and use the concept of conservation of energy

2. What is Work? Section 5.1 Work is a transfer or conversion of energy
transfer occurs when a force is applied in the direction of the force force = mass x acceleration (g)
conversion occurs from one form of energy to another
mechanical, thermal, electrical, radiant, nuclear and chemical
W = F x d W = F x d cos θ

3. Simple Machines demonstrate the concept and calculations of Work
Simple Machine- device that makes work easier
multiply force OR distance
Increasing force or distance are at the expense of the other variable
Energy is conserved in an ideal situation no friction
Work in would equal Work out in another words F x d (in) = F x d (out)
Work in is done on the machine and Work out is done by the machine

4. R ---2m-----f--------4m------- E
MA = 2
R= 40N f E = 20N
MA = Fr / Fe or
MA = Xe / Xr
Levers include 1st, 2nd, 3rd, classes, wheels and axels and pulleys
Pulley- grooved wheel and a rope MA= the number of strands supporting resistance

5. Inclined Planes include ramps, wedges and screws
Gears- toothed wheels MA = ratio of teeth of each gear increase force or speed of rotation
Efficiency- ratio of work out to work in
eff = W out / W in

6. What is Energy? 5.2 Energy – ability to cause a change
to do work work = transfer of energy
6 forms of energy and two states of energy
Kinetic – motion
W = F x d
= m x a x ΔX a ΔX = vf² - vi² / 2
= m x vf² - vi² / 2
= ½ m v²
increase mass vs increase velocity v²

7. Work – Energy Theorem
transfer of energy by a force through a distance
transfers Kinetic Energy
Work = ΔKE
= KE f – KE i
Units KE = ½ mv²
= kg m²/s²
= N m
= J

8. What is Potential Energy?
Potential Energy – state of energy where a change is stored
position relative to a measured height
gravitational potential energy
PE = m g h weight = m g
= kg m/s² m = N
= N m
= J

9. Elastic potential energy – energy stored in an object stretched or compressed
Spring ex. spring scale
PE elastic = ½ k x²
k = spring constant
x = distance stretched

10. How is Energy Conserved ?
Conserved – energy is not gained or lost within a system
only converted or transferred
Mechanical Energy is the sum of the KE and the PE in a system
the exception is friction that converts some ME into heat that is nonmechanical
ME i = ME f KE + PE = KEtotal
½ mv² + mgh = ½ mv² + mgh
ex. Falling rock PE to PE+KE to KE

11. What is the Rate at which work is done?
Power – the rate at which work is done or energy converted or transferred
P = ΔW / t
= F x d / t
= F x v
mgh / t or ½ mv² / t
units P = W / t
= J / s
= watts w = kw
1 hp = 746 w

12. YOU have the POWER
To get the WORK done
And
Accelerate on this next Exam