1. Class Notes 4.19.11
Mechanical Energy and Work
Equation Sheet
HW: 3 sheets
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=345
Retake TEST by Thursday 4.21.11
Hw LATE -50%
Twin Towers worksheet Late -40%
Bouncing ball lab
is due
Thursday by 3pm.
Staple all 3
packets together
in order
List for sports
bus for Twins

2. Calculate the Potential energy from the drop
height and the bounce height
page 5 space 4
Always
positive!

3. Use the average height for PE
be ball #1 m = ____ grams= ______kg
(change heights to meters)
Drop
Height hD
(m)
Average
Bounce
Height hB
(m)
Drop
PED
=mghD
(Joules)
Bounce
PEB
=mghB
(Joules)
Δ PE
(PEB
-PED
)
(Joules)
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60

4. What is energy slide

6. Mechanical Energy

7. Mechanical Energy
• The energy acquired by the objects upon which work
is done is known as mechanical energy.
• Mechanical energy is the energy which is
possessed by an object due to its motion or its stored
energy of position. Mechanical energy can be either
KE (energy of motion) or PE (stored energy of
position).

8. An object which
possesses
mechanical energy is
able to do work.
• In fact, mechanical energy is often defined as
the ability to do work. Any object which
possesses mechanical energy - whether it be in
the form of PE or KE - is able to do work.
• That is, its mechanical energy enables that
object to apply a force to another object in
order to cause it to be displaced.

9. An object which possesses
mechanical energy is able to do work.
Gravity
moved
the mass
down!!
Notice
how the
spike
moved
faster

10. Energy transactions with the bouncing ball lab.
If COR =1
The force
squashed
the ball!!

11. Energy transactions with the bouncing ball lab.
If COR <1
The force
squashed
the ball!!
And
energy is
lost to
T.M.E.

12. Mechanical Energy Equations
Always
positive!
Page 5 space 5

13. Mechanical Work Equations
in any direction
Page 5 space 6
Always
positive!

14. Mechanical Work Equations
Page 6 space 1
Moved
vertically
Always
positive!

15. Mechanical Power Equations
POWER –how fast work is done
Page 6 space 2
Always
positive!

16. Mechanical Power Equations
POWER –how fast work is done
Page 6 space 3
Always
positive!

17. Work Time
• Labs due Thursday
• Try the worksheets you have.
• We will continue with this topic tomorrow.
• Lab on THURSDAY??
• Possible Quiz Thursday on Equations