Wednesday PS Notes 11-6

Homework

Rube Goldberg machines

Conservation of energy

Homework

• Handout

Equation review on P1 prob 1-7

Energy Review on P2 prob 1-9

KE = ½mv2 GPE = mgh

m = mass (kg) g = acceleration (9.8)m/s2

v = velocity (m/s) h = height (m)

Answers

1) A. 490,000 J b. 5,600,000 Jc. 280,000 J

2) 1.4 x 1015 J3) h= 15 m4) m = 58 kg5) a. 630,000J b. 240,000 J, c. 110,000 J6) v = 3.3 m/s7) m = 8.0 kg

Answers P2

1) KE, EPE, GPE, CE, TE, EE, LE, NE

2) Energy is the ability to do work, Work is the result of transferring energy

3) Potential = stored e

Kinetic = motion e

4) a. KE, GPE b. CE, GPE c. EPE, GPE

d. LE e. GPE

Answers P2

5) Has GPE, to be transferred, when needed to move the water (using the force of gravity)

6) Water tank, Hanging by finger from ledge of cliff

Math skills on P2

Simplified Pencil Sharpener

Pencil Sharpener description

• Open window (A) and fly kite (B). String (C) lifts small door (D) allowing moths (E) to escape and eat red flannel shirt (F).

• As weight of shirt becomes less, shoe (G) steps on switch (H) which heats electric iron (I) and burns hole in pants (J).

• Smoke (K) enters hole in tree (L), smoking out opossum (M) which jumps into basket (N), pulling rope (O) and lifting cage (P), allowing woodpecker (Q) to chew wood from pencil (R), exposing lead.

• Emergency knife (S) is always handy in case opossum or the woodpecker gets sick and can't work.

How to keep a shop window clean

Description for shop window

• Passing man (A) slips on banana peel (B) causing him to fall on rake (C).

• As handle of rake rises it throws horseshoe (D) onto rope (E) which sags, thereby tilting sprinkling can (F).

• Water (G) saturates mop (H). • Pickle terrier (I) thinks it is raining, gets up to run into

house and upsets sign (J) throwing it against non-tipping cigar ash receiver (K) which causes it to swing back and forth and swish the mop against window pane, wiping it clean.

• If man breaks his neck by fall move away before cop arrives.

For each Picture!• Break down each Rube Goldberg Machine into a list of action in

sequence

• For each action, list any type/form of energy that is associated with the action

• For each energy type/form, state whether it is gained or lost as a result of the action

• Describe any simple machines associated with the action. For all machines, indicate input and output force

• For your favorite rube, list all objects that undergo work. Name the force which does work on object. Indicate which object had the most work done on it

Steps and energy connectionsSteps KE GPE EPE CE OTH

Kicking Paddle

Lowering finger

Turtle extending head

Tong separation

Dropping pillow

Draw arrow for each in each energy box, indicating if that type of energy is increasing because of action.

Steps and simple machines

Steps Type of Machine

Input Force

Output Force

Kicking Paddle Man’s leg

___ lever

Muscle Leg on Paddle

Lowering finger

Turtle extending head

Tong separation

Dropping pillow

Steps and energy connectionsSteps KE GPE EPE CE OTH

Draw arrow for each in each energy box, indicating if that type of energy is increasing because of action.

Steps and simple machines

Steps Type of Machine

Input Force

Output Force

Conservation of Energy

• Take any action step on the last assignment

• Are all the types of energy increasing or descreasing in amount

• Where’s the energy coming from or going to?

Conservation of Energy

Conservation

• Does not mean that we are Not trying to waste energy or reduce the amount we use

• Means that for a closed system the amount of energy in the system is constant at all times

Systems

• A system is composed of 1 or more objects that have a connection to each other

• CLOSED system = No energy is lost

• OPEN system = Energy is lostgained in relationship to the non-included environment

Formal definition of

Conservation of energy• For a closed system:

• Energy can not be created or destroyed, only transferred or transformed.

Example of open systems

• The earth (exchanges energy with the surrounding space)

• A roller coaster (losses heat, sound to the surrounding air)

Roller Coaster Project

• 2 parts

Performance Part

Analysis Part

Read Pg 11,12Read answer questions on page 20-22