Energy ChainsCan you think of how the energy

flows through a car? What would you start with? What types of energy

transformations are happening?

Energy Transfer and Transformation

Chemical

Electrical

ThermalMechanical

Kinetic Energy

Thermal Energy

Can you construct an Energy Chain for a

person hitting a softball to the

outfield?

Hitting a softball into the outfield

1. Chemical E to pick up bat from food.

2. Ball has PE in the air3. Ball throw in air

transform from PE to KE

4. Bat hits ball transfers KE to ball

5. Ball increases KE6. Gravity pulls on ball7. Air resistance slows

ball down

8. Ball hits ground (Friction)9. Balls KE is transferred to dirt

as it flies up.

Constructing Energy Diagrams

Using Font SizePredict what this car is doing?

Coming to a stop!The KE is deceasing over time as it is being

transformed in heat and PE energy.

A car stopping as a standard Bar Graph

KE HE

Using Circle GraphsCircle graphs can be used to illustrate energy flow. Each form is a represented by a portion of the circle. Multiple circle graphs can illustrate how the amount of energy in each form changes over time.

Circle GraphExamine what is happening in these

circle graphs?

What do you notice at interval 4?

ENERGY CHAINSLet’s look at some systems where

energy transformation is taking place…(i.e. changing from one type of energy to another type of energy.)

RampsCarsBungee jumperA PendulumA Hydroelectric Power Plant

Energy RampLabel sections A-E w/ the appropriate level of PE and

KE

(Assume NO friction)

Use the following terms

Maximum

High

Medium

Low

Minimum

PE= Max

KE=Min

KE= Max

KE= High

KE= Low

PE= High

KE= Med

PE= Min

PE= Low

PE= Med

PENDULUM

E

C

B D

A

At which point is the KE greatest?

What is the velocity at that point?

Point C

5.6 m/s

Pendulum Energy Transformation

Draw this pendulum diagram on white board

A. PE=KE?Points 2 and 4B. PE greatest?Points 1 and 5C. KE greatest?Point 3 onlyD. KE lowest?1 and 5E. PE lowest?3 only

1. Statement: The farther above the ground an object, such as a book, is raised, the greater the object’s Gravitational Potential Energy (GPE).Circle the statement below which most closely matches

your thinking and then explain your thinking.

1.Yes, everything has some potential energy.

2. Yes, but it only gets potential energy when it falls.

Yes, because gravity is stronger the higher you go up.

3. Yes, one thing that determines the GPE is the distance between the object and the ground.

4. No, there is no force or motion happening.

5. No, it is not in contact with anything which could give it energy.

POTENTIAL energy (PE)

Potential Energy (PE) is the stored energy of an object resulting from the position of the object in a system.

PE is measured by multiplying the mass of the object times the gravity and then times the height.

PE = m x g x h remember…(gravity = 9.8m/s2)

Units are Joules!!! (J)1 Joule= 1kg x m2/s2

POTENTIAL energy (PE)

Examples of objects with high PE:

A stretched rubber bandAny hanging objectAny compressed object (like a spring)Any object that is high up

PE Power Triangle

Plug PE = m*g*h into a Power Triangle

Write the equations when you solve for m and h.

A mountain biker rides down a 42m high mountain with 2500 J of GPE. What is the

mass of the mountain biker?

D U F A S

PE=2500

m=?

g=9.8

h=42

J

Kg

m/s

m

PE=m*g*h

m= PE/(g*h)

m= 2500J/(9.8m/s * 42 m)

m= 6.07 kg

Scientific NotationThink about the number line:

Scientific NotationWhen you see a number like:3.46 E-4 m Come up on your

calculator…

Here’s what that means…

Scientific Notation3.46 E-4 … The E-4 means x10-4

And here is how you translate that into a number. The exponent (-4) tells you how many times to move the decimal point (4).

And because it is negative (-), to move it left!)

Scientific NotationSo for 3.46 E-4 g

You will move the decimal point 4 times to the left. (negative is to the left on the number line!!!)

= .000346gMake sure you put units on it also! =.000346g

Scientific NotationLet’s practice:

Change 4.86 E3 kg into a regular number…

Need to move the decimal 3 times and to the right because the 3 is positive.

= 4860 and don’t forget units!= 4860 kg

Scientific NotationYOUR TURN:1.) 9.325 E-2 m2.) 2.1903 E4 kg3.) 7.473 x10-6 g4.) 3.801 x105

cm3

ANSWERS:1.) .09325 m2.) 21903 kg3.) .000007473

g4.) 380100 cm3

Solving Energy Problems

pg 299 (1-4)

m = PE h = PE

g*h g*m

kilo hecto  deka  gram 

deci  centi  milli 

kg hg dg g dg cg mgkilogra

mhectogra

mdekagra

m gramdecigra

mcentigra

mmilligr

am

1,000 100 10 1 0.1 0.01 0.001

MASS