Unit 9 Flashcards
What is energy?
A measurement of an object’s capacity to change things around it.
It is the ability to exert a force on an object while it moves through some distance in the direction of the applied force.
What is the property of energy associated with?
Force and an object’s position or motion
How many general types of energy are tehre?
Two
What are the two general types of energy?
- Potential energy
- Kinetic energy
What is potential energy?
Energy that depends on the position of an object or the positions of its parts.
What is kinetic energy?
Energy that depends on an object’s motion
What are potential and kinetic energy broken down into?
Mechanical or internal energy
What’s another name for mechanical energy?
Macroscopic (objects we can see, not atoms or molecules)
What’s another name for internal energy?
Microscopic (atoms and molecules)
What is mechanical energy?
A name given to the kinetic or potential energy of LARGE macroscopic objects
What is internal energy?
A name given to energy hidden within matter, but manifest by the object’s temperature, shape, physical state (gas, solid, liquid), the chemical composition, etc.
What are the two units of measurement?
Joule
or kWh (kilowatt hour)
What is the formula for kinetic energy at low speeds?
Kinetic energy = 1/2mass x speed^2
What two things does kinetic energy depend on?
Mass and speed
True or False: Kinetic energy of an object can have an absolute value.
False.
Because it depends on speed, which is relative.
What is gravitational potential energy?
The energy stored in an object that has the potential to fall.
Near the surface of Earth:
GPE = weight x height
True or False: Gravitational potential energy is relative.
True, because it depends on height, which is relative
True or False: The gravitational force between two objects decreases with distance, but the gravitational potential energy increases with distance.
TRUE
Why does GPE increase with distance?
Because the farther apart objects are, the faster they will move when they come back together and the more kinetic energy they will gain
Why are asteroids and comets so dangerous?
Because they gain energy - and therefore greater destructive power - by falling from long distances (through the earth’s atmosphere)
What is electrical potential energy?
Greater charge creates more electrical potential energy.
The EPE for opposite charges is the greatest when the charges are far apart.
EPE for the same charge (+ or -) decreases as the charges become farther apart, and is strongest when they are close together.
What does “work” mean in science?
Refers to energy transferred as an object is moved in the direction of an applied force.
It is a process of transferring or transforming energy.
What is the formula for work?
Work = force x distance parallel to the direction of the force
True or False: A student does “work” to a 70lb backpack while walking to class.
FALSE
The force is perpendicular (force up on backpack, walking horizontally)
How could a student do work to a backpack?
Change its speed or change its height
True or False: Work is a form of energy
False
What is the process that describes potential energy turning into kinetic energy?
Work
What is thermal energy?
Total kinetic energy of random motion of molecules in a material.
What type of energy depends on the positions and motions of the atoms and molecules that make up objects, rather than the position or motion of the entire object?
Internal energy
True or False: When energy seems to vanish, it tends to end up as heat.
True
Why doesn’t a bouncing ball go up to the same height it started from?
Because air friction and the effects of the bounce transformed some of its potential energy into thermal energy - heat.
The ball is slightly warmer than when it was dropped.
Perpetual motion machine
A machine that keeps moving forever without any energy being added.
Why are there no perpetual motion machines?
Because energy transforms into thermal energy.
What is heat transfer?
The transformation of heat behaving in a way similar to a fluid, moving from one form to another
What are the three ways heat is transferred?
- Conduction
- Convection
- Radiation
What is conduction?
It takes place when objects having different temperatures come into direct contact with each other. The energy moves from the hotter object to the cooler one.
Energy transfers BECAUSE of the difference in temperature.
Matter is a stationary conduit through which the heat moves.
What is an example of conduction?
Burning your hand on the stove
What is convection?
Takes place when hot material moves and transfers its heat to colder material.
What is an example of convection?
Firefighters carrying a bucket of water to put out the fire. Each one has a bucket.
Or a baseboard heater that raises the temperature of the air around them. That hot air rises and cool air replaces the space around the heater. The cycle continues.
What is radiation?
A process where thermal energy is transmitted by visible light, infrared radiation, UV radiation, x-rays, or radio waves.
What is an example of radiation?
The sun heating the earth through millions of miles of empty space.
True or False: Atoms have different amounts of energy depending on how they are bonded together.
True
What is chemical potential energy?
Energy associated with, or within, chemical bonds.
Is chemical potential energy internal or mechanical?
Internal, deals with atoms
Is elastic potential energy internal or mechanical?
Internal, deals with atoms
What is elastic potential energy?
The form of internal energy associated with stretching or compressing material
How does elastic potential energy work?
You are storing energy as you move the molecules of a rubber band farther apart than they were in equilibrium. If you let go, the force pulling the molecules back to their equilibrium position converts this stored energy into kinetic energy.
True or False: Elastic potential energy is also the energy used to describe the compression of carbon dioxide within a whipped cream can.
True
Compression AND stretching
What is nuclear potential energy?
Energy stored in the nucleus of an atom BECAUSE of the strong force between nucleons.
It is about the positions of protons and neutrons in a nucleus.
What two competing forces work within the nucleus of an atom?
Strong force and EMG force.
Strong force holds its protons and neutrons together, EMG pushes protons apart.
True or False: It is impossible to travel faster than the speed of light.
True, Gedanken experiment proved this
True or False: Mass is related to energy. Mass increases with more energy (speed).
True
True or False: An object emitting light would lose mass proportional to the energy it radiates away.
TRUE
What is the E = mc^2 equation for?
Einstein’s equation to show how mass and energy were related at the speed of light.
True or False: If something is moving fast, it has more energy, so it has more mass.
True
True or False: If you slow something down by exerting a force on it, you are doing work, and transferring energy away from the object. But as long as the energy is still there, so is the mass, regardless of what form the energy takes.
TRUE
True or False: The energy of any object - whether it is kinetic, potential, or any kind of internal energy - will be manifest as mass.
TRUE
What is the law of conservation of mass-energy?
The total amount of mass and energy remains the same. Energy can change forms, and mass can change into energy and vice versa.
Happens at high speeds (at least, significantly measurably at high speeds)
What is “work”?
When energy is transformed or transferred by forces acting on an object.
What is thermal energy?
Energy associated with temperature.
What does the word “potential” tell you about the type of energy?
It is associated with position
True or False: Bringing objects that are attracted to each other together, decreases their energy, including chemical reactions.
TRUE
True or False: An object has more thermal energy when it is warm.
True
How is chemical potential energy released?
When the chemical composition changes.
Which type of energy is the most concentrated, and what does that mean?
Nuclear
Largest amount of energy in smallest volume
True or False: Potential kinetic energy is a thing.
FALSE
nope.
What type of energy can conduction, convection, and radiation transfer?
Thermal energy
What type of energy does “work” deal with?
It can be thermal but doesn’t have to be.
True or False: In order for work to occur, there must be a force acting upon an object.
True
What MUST be included for “work” to be done?
Motion in the direction of the force.
What does the law of mass-energy state about mass and energy?
They are two manifestations of the same quantity.
What does “using” energy mean?
One type of energy is transformed into another.
