Kinetic and Potential Energy3

Where did James Joule work?

At his family brewery in England

In Joules spare time what did he do?

Tinkered with electric motors

What did Joules propose a connection between?

The work a motor does and the heat it produces

Work and heat are different forms of energy measured in what?

Joules

Who quantified Joules idea?

William Thomson

What honorific title did William Thomson go by?

Lord Kevin

Joules ideas turned into what?

The laws of thermodynamics

Ideas about heat and energy were born from what?

Practical concerns about how to make more efficient machines

Joules measurements in his experiment confirmed what?

That the missing energy of the falling weight could be accounted for in the warming of the water

Why is energy difficult to define?

It is applied to so many things, in a sense everything is energy

How is describing a system in terms of energy useful?

We can be certain that the total amount of energy in a closed system always remains the same

What can we can say about the total number of joules in a close system up to and including the universe?

It never changes

The idea of the conservation of energy is often phrased as what?

Energy cannot be created nor destroyed

Everything in the universe can be thought of as what?

One object giving energy to another

How do objects transfer energy?

Through the fundamental forces

What is kinetic energy?

The energy something has when it is moving

If you throw a baseball with 10 joules of energy where does the energy come from?

The energy stored in your muscles, which you got from the food you ate, whatever food you ate got its energy from the bottom of the food chain which got its energy from sunlight

Where does the sun get its energy from?

Nuclear reactions in its core which fuse hydrogen atoms together to create helium

The energy stores in hydrogen atoms has been around since when?

The beginning of the universe (often referred to as the Big Bang)

When a baseball that was thrown hits the ground, where does its energy go?

Some into the air creating the sound of the impact, some into the ground sending vibrations, some into the baseball itself compressing it as it landed

Which concepts go hand in hand?

Heat and energy

What is heat?

Energy in transit between objects that are at different temperatures

True or False, a substance does not emit or absorb heat, it contains it

False, A substance only emits or absorbs heat

What did scientists previously believe about heat being exchanged between substances?

That it was its own substance known as phlogiston

What did more precise combustion reveal about the idea of phlogiston

Heat is not a separate substance, but rather is a property already inherent in the materials

What does temperature describe?

The average kinetic energy of the atoms of a substance

For substances at higher temperatures, on average how are atoms moving?

Faster

The combined kinetic energy exchange between all the atoms in a substance is called what?

Heat

What is the second law of thermodynamics?

Heat always flows from high temperatures to low temperatures

What law explains why if a red ball were to hit a green ball, then the red ball will feel an equivalent reaction force back on it?

Newtons third law of motion

Macroscopically we say that heat flows between substances until what?

They are the same temperature

The temperature that heat will stop flowing is between what?

The two starting temperatures

What is the third law of thermodynamics about?

Absolute zero temperature

What does the third law of thermodynamics say?

No substance can ever actually reach absolute zero

If you wanted to cool a piece of metal to absolute zero what would you need to do?

Submerge it in a substance below zero which does not exist

In addition to kinetic energy and heat, what is another form of energy?

Gravitational potential energy

What is gravitational potential energy?

The energy that an object possesses due to its position in a gravitational field such as Earth’s

If you toss a stone up into the air what slows it down?

Earths gravity

As a stone that is tossed into the air loses kinetic energy what does it gain?

Gravitational potential energy

A pendulum swinging back and forth is a exchange between what?

Kinetic and potential energy

At the lowest point of a pendulums swing, what can be said about its energy?

Its moving its fastest and at maximum kinetic energy

As a pendulum reaches its highest points what is at its maxiumum?

Gravitational potential energy

When a pendulum swings what remains constant?

The combined kinetic energy and gravitational potential energy

What varies as a pendulum swings?

The amount of energy that is kinetic energy, and the amount that is potential energy

What can we think of potential energy as?

Energy that can readily turn into kinetic energy

Even though potential energy is potential why wont it become energy?

It is energy

As a brick slides along the ground what will slow it to a stop?

Friction

The kinetic energy from the brick sliding against the ground is turned into what?

Heat

How can we turn the heat back into kinetic energy?

By making the brick move again

Friction can only do what?

Slow things down

What is not associated with friction?

Potential energy

Similar to gravitational potential energy, what other potential energy exists?

electric potential energy

How does electric potential energy work?

The same as gravitational but via the electric force rather than gravitational force