1. Quiz B
A stone of mass m is thrown straight upward with an initial velocity V0. Find the change in gravitational potential energy (ΔPEg) of the stone between points
A and B (PEgB – PEgA) = mgh
B and C (PEgB – PEgC) = - mgh
A and C (PEgC – PEgA) = 0 V0 A m C

2. Energy Gravitational Potential Energy PEg Kinetic Energy KE
Spring Potential Energy PEs
Energy
Need play dough and a block

3. ΔKE = W Kinetic Energy KE Mass F Velocity 2aΔx=vf2 – vi2
F=constant d
F=Mass × Acceleration
2aΔx=vf2 – vi2
KEf – KEi = Fdcosθ
KEf – KEi = Fd
2ad=vf2 – vi2
KEf – KEi = mad
KEf – KEi = ½ m(vf2 – vi2)
Need play dough and a block
KEf = ½ mvf2

4. KE = ½ mv2 Kinetic Energy KE Zero Kinetic Energy?
Need play dough and a block
Depends on a frame of reference!!
Negative Kinetic Energy?
Never!!

5. in gravitational potential energy (ΔPEg) of the stone
final h
A stone of mass m is thrown straight upward with an initial velocity V0. Find the change
in gravitational potential energy (ΔPEg) of the stone
in kinetic energy (ΔKE)
In total energy, potential + kinetic (ΔE)
Kinematics:
h = V02 /2g
ΔPEg = PEgf – PEgi = mgh – 0 V0
ΔKE = KEf – KEi = 0 – ½ mV02
initial
ΔE = Ef – Ei = 0 m

6. A stone of mass m is dropped from height h. Find the change
initial m h
A stone of mass m is dropped from height h. Find the change
in gravitational potential energy (ΔPEg) of the stone
in kinetic energy (ΔKE)
in total energy, potential + kinetic (ΔE)
Kinematics:
h = Vf2 /2g
ΔPEg = PEgf – PEgi = 0 – mgh
ΔKE = KEf – KEi = ½ mV02 – 0
final
ΔE = Ef – Ei = 0 Vf

7. Energy Bar charts Work-Energy representation
A bar represents each type of energy in the system:
initial and final.
There is a bar to represent work done by external objects on the system. + -
Before
After
KEi
PEgi
KEf
PEgf W
PEsi
PEsf
The work bar is shaded to indicate that it is not a type of energy but is a process involving an interaction between a system and an object outside the system.

8. ΔE = W 1. Define a system 2. Define the initial and final states
3. Draw an Energy Bar Chart (Work?!)
4. Write the Energy-Work Formula
ΔE = W + -
Before
After
KEi
PEgi
KEf
PEgf W
PEsi
PEsf

9. Friction ΔE = W 1. Define a system
2. Define the initial and final states
Friction
3. Draw an Energy Bar Chart (Work?!)
4. Write the Energy-Work Formula
ΔE = W + -
Before
After
KEi
PEgi
KEf
PEgf W
PEsi
PEsf V0
stop μk
X-? μs

10. Pendulum ΔE = W 1. Define a system
2. Define the initial and final states
3. Draw an Energy Bar Chart (Work?!)
4. Write the Energy-Work Formula
ΔE = W + -
Before
After
KEi
PEgi
KEf
PEgf W
PEsi
PEsf 1 3 2

11. Roller Coaster ΔE = W 1. Define a system
2. Define the initial and final states
Roller Coaster
3. Draw an Energy Bar Chart (Work?!)
4. Write the Energy-Work Formula
ΔE = W + -
Before
After
KEi
PEgi
KEf
PEgf W
PEsi
PEsf

12. A hockey puck slides without friction along a frozen lake toward an ice ramp and plateau as shown. The speed of the puck is 4m/s and the height of the plateau is 1m. Will the puck make it all the way up the ramp?
A: Yes
B: No
C: Need more information
h = 1m
v = 4
m/s

13. Homework Read 5.1, 5.2, 5.3, Examples!!! MC 5, 6, 7, 10
Problems # 8, 25, 30, 41, 43, 46
Homework
Due Friday

14. A hockey puck slides without friction along a frozen lake toward an ice ramp and plateau as shown. The height of the plateau is 2m. With what speed should the puck slide to make it all the way up the ramp?
Quiz
h = 2m
V – ?