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

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

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

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!!

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

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

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.

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

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

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

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

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

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

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 – ?