What is that…

The bowling ball pendulum of death sat suspended in midair, the tension of the supporting cable analogous to the tension in the air. Is it art or science, this bowling ball? What secrets of the natural world lay trapped inside this bowling ball pendulum, and how would such secrets become revealed? And why would anyone in his right mind suspend a bowling ball from the ceiling? Surely, this was the work of a madman.

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Introduction to Energy

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For the most part here we will be concerned with the study of mechanical energy. By this we mean that we will be considering the energy concepts associated with everyday life.

We are all familiar with energy, so in your notebook, write down what it is we mean by energy! (what is energy?) How is energy responsible for the consequences of the bowling ball of death

The story so far….

• Distance (displacement) is change in position (m) • Velocity is change in position with time (m/s) • Acceleration is change in velocity with time (m/s 2 ) • Mass is a measure of how much matter (kg) • Force is needed to accelerate an object (N) • Momentum is a measure of inertia in motion (kgm/s) • Force x time changes momentum (impulse) • Next concept is Energy and Work.

K i n e t i c a n d P o t e n t i a l E n e r g y

Objectives

• You will be able to define and identify Kinetic and Potential energy.

• You will be able to calculate kinetic and potential energy.

• You will be able to give examples of the two forms of energy.

• You will be able to explain how one can transfer to the other.

Objectives continued…

• You will be able to define and calculate work.

• Describe what determines the power output of a system.

• Apply the law of conservation of energy to explain the motion of an object.

Vocabulary terms, you may know now…you will know later!

• Energy • Joule • Potential Energy • Kinetic Energy • Law of conservation of energy

Definition of Energy…

The ability or capacity to do work.

Measured by the capability of doing work:

potential energy

or

the conversion of this capability to motion: kinetic energy.

Potential Energy…

• Energy due to position or

stored energy.

Measure by: PE= (mass) (gravity) (Height) Potential energy is calculated by: The object’s mass, multiplied by the earth’s gravitational pull (10 m/sec sq), multiplied by the distance the object can fall.

PE = mgh

• • •

m = mass (kg) h = height (m) g = accel due to (gravity 10 m/s 2 )

Examples of Potential Energy:

Stretching a rubber band..

-Stores energy Water at the top of a waterfall..

-Stores energy Yo–Yo in held in your hand..

-Stores energy because of position Drawing a Bow… -Stores energy because of position

• When the position of an object is

altered it, creates Potential Energy.

• A yo-yo on the table, doesn’t have energy,

but when picked up, it alters its position and now it has the ability (or potential) to do work.

• A bow doesn’t have the capacity to do

work, unless it’s held at an elevated position.

Summary of Potential Energy

• Energy that is stored and waiting to be used later

Definition of Kinetic Energy…

The energy of motion.

Measured by: KE= ½ (Mass) (Velocity)

2

Kinetic energy is calculated by one half of the object’s mass, multiplied by the object’s speed- squared.

Examples of Kinetic Energy…

• Shooting a rubber band.

• Water falling over the fall.

• A Yo-Yo in motion.

• Releasing the arrow from the bow.

Potential Energy Converted to Kinetic Energy…

When stored energy begins to move, the object now transfers from potential energy into kinetic energy.

Standing still Running

What is Kinetic Energy?

o Energy an object has due to its motion o K.E. = .5(mass x speed 2 )

Summary of What You’ve Learned..

Example using a coin:

• Holding a coin in you hand, alters the coins

original position.

• The coin has potential energy, because it

has ability to do work.

• Dropping the coin in the bank, changes the

stored energy into motion.

• This transfers the coin’s energy from

potential to kinetic energy.

Follow Up Homework…

• At home, find at least 10

objects.

• You will take these objects

and test to see which has Potential and Kinetic energy or both.

• Make a chart or table

similar to the one here to organizing your data.

• Be creative with the

objects you choose, and make sure you understand your results to present to the class.

Potential Energy Example Example Example Example Kinetic Energy Example Example Example Example Both Example Example Example Example

Just 1 more thing

• We have learned all about Potential Energy and Kinetic Energy so far… • But they fall under 1 big form of energy… • Mechanical Energy

What is Mechanical Energy?

o Energy due to a object’s motion (kinetic) or position (potential).

The bowling ball has mechanical energy. When the ball strikes the pins, mechanical energy is transferred to the pins!

Examples of Mechanical Energy

Cliff Hanger…(pun intended)

See the Potential Energy!!!

• Still to come..

• Practice calculating different types of energy • Calculating Work • Understanding and calculating Power • Are you more powerful than a horse?

T h e E n d .

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