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Chapter 5
Chapter 5 Section 4
Objective- Wait to copy this until
next time we meet.
• We will learn about:
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–
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Power
Work
Energy and
The conservation of energy
Warm-Up
• No Warm Up
1
Power- the rate @ wh.
Work si done or energy is
transformed
Since W = F x d
then…
And D/T = Velocity
SO…..
3
P=Fv
2
Example
• A 193kg curtain needs to be raised 7.5m, at
constant speed, in as close to 5.0sec as
possible. The power ratings of three motors
are listed as 1.0kW, 3.5kW, and 5.5kW. Which
motor is best for the job?
Exit Ticket
• HW: Pg
181
1,3,4
• Hint: #1 Force is going to be ( mg + Fk)
• Hint: #3 Work= mgd
Chapter 5 Section 1 and 2
Objective
Warm-Up
• We will learn about:
• Get out HW, we will check it
–
–
–
–
Power
Work
Energy and
The conservation of energy
Work- is done on an obj. when a
Force causes a displacement
Units: Work (Joules or J)
Force (N)
Displacement ( m)
This formula is when work is
parallel to displacement
I don’t really like to s
W= F d Cos theta
Sign of Work
Displacement will determine sign of work
+ work done ON obj (force is in direction of
motion)
- Work done BY obj (force is opposite to motion)
Sample problem Pg 161
Energy
Kinetic Energy (KE)
*Obj in motion
*Speed and mass matter
*W net= KE
Potential Energy
* Energy due to obj’s height,
position from zero level
Relaxed
x
compressed
m=mass in kg
V=velocity
Sample problem B, C, D
M=mass in kg
H=height
K=spring constant
X=distance compressed or stretched
Exit Ticket
• HW: Pg 162 #3 AND 163 #1 and #3
Lab Day
Objective
Warm-Up
• We will learn about:
• Get out HW, we will check it
–
–
–
–
Power
Work
Energy and
The conservation of energy
Exit Ticket
HW:
• PG: 166 #3
• PG 168 # 1
• PG 172 #1 and 3a only
Chapter 5 Section 2 and 3
Objective
Warm-Up
• We will learn about:
• Get out HW, we will check it
–
–
–
–
Power
Work
Energy and
The conservation of energy
• Finish section 2 if needed
Conservation of Energy
• Conservation of energy is the same as
constant: The law of conservation of energy
(energy cannot be created nor destroyed) is
the same as the law of constant energy
• Mechanical energy is not the same as nonmechanical energy( wh is nuclear, chemical,
electrical)
PE can also come from both a spring and
gravity in which case it would be the SUM
of PE
ME initial = ME final
ideally ALL PE turns into KE BUT the reality is because we always have
friction this does not happen.
Energy is not LOST it is just converted.
Remember energy cannot be created nor destroyed
Sample Problem E
Exit Ticket
HW:
• PG: 177 #1 and #2
• PG 178 # 1
Review Day
Objective
• Review for test
Warm-Up
• Get out HW, we will check it