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Bozarth Unit Test - Study Guide
Terms in this set (49)
What is energy?
the ability to do work or cause change
How are energy, work, and power related?
Energy and work are measured in the same unit (joules). When work is done on an object, energy is transferred to the object. The amount of energy transferred or work done in a unit of time is power.
If a handsaw does the same amount of work on a log as a chainsaw does, which has more power? Why?
The chainsaw has more power because it transfers energy to the log faster than the handsaw
What is kinetic energy? Give examples.
Kinetic Energy is the energy that an object has due to its motion. Some examples are: 1) A ball rolling 2) A car moving 3) A penny flying at your head
What is potential energy? Give examples.
Potential Energy is stored energy that results from the position or shape of an object. Some examples are: 1) A ball on a slope 2) A stretched rubberband 3) A penny in a pulled back slingshot
What factors affect an object's kinetic energy?
Mass and Velocity
At a given height above Earth, how would you determine the potential energy of a skydiver? The kinetic energy of a skydiver?
You would need to know the sky diver's weight, height above the
Earth's surface, mass, and velocity.
-Potential energy = weight x height above Earth's surface
-Kinetic energy = ½ x mass x velocity
What is mechanical energy?
Mechanical energy is kinetic energy or potential energy associated with the motion or position of an object AKA sum of kinetic and potential energy in an object
If the kinetic energy of a falling apple is 5.2 J and its potential energy is 3.5 J, what is its mechanical energy?
Its mechanical energy is 8.7 J, the sum of its potential energy and kinetic energy.
If an object's mechanical energy is equal to its potential energy, how much kinetic energy does the object have? How do you know?
Its kinetic energy is zero because mechanical energy equals potential energy plus kinetic energy.
List the five forms of energy associated with the particles that make up objects.
Why do the particles of objects have both kinetic and potential energy?
These particles are constantly in motion, so they have kinetic energy. The particles also have potential as the result of their specific arrangement in objects.
What kind of energy do you experience when you eat a peanut butter and jelly sandwich?
Mechanical when you chew the food
Chemical when the food gets broken down by saliva and enzymes
Kinetic because the food is moved around the mouth, swallowed
What is the relationship between different forms of energy?
Most forms of energy can be transformed into other forms
When you turn a toaster on, what happens to the electrical energy?
The electrical energy is transformed into thermal energy and electromagnetic energy.
Describe the energy transformations that happen when you strike a match. List them in the order in which they occur.
Striking a match transforms mechanical energy to thermal energy. The thermal energy causes particles to release chemical energy.
Chemical energy is transformed to thermal and electromagnetic energy.
What common energy transformation allows you to send a rubber band flying across the room?
Elastic potential energy in the stretched band is transformed into kinetic energy.
Describe the energy transformations that occur when you bounce a ball.
As the ball falls, potential energy is transformed to kinetic energy.
While the ball is in contact with the floor (during the bounce), kinetic energy is transformed to elastic potential energy, which is transferred back into kinetic energy. As the ball travels upward, kinetic energy is transformed into potential energy. Some kinetic energy is transformed into thermal energy / sound during the
Describe the energy transformations that occur in the pendulum.
Downswing - potential energy is transformed into kinetic energy
Upswing - kinetic energy is transformed into potential energy
State the law of conservation of energy in your own words.
No energy is created or destroyed as one form of energy is transformed into
Thermal energy is produced when a firefighter slides down a pole. Where does it come from?
Some of the firefighter's potential energy is transformed to thermal energy through friction.
Based on the theory of relativity, what must always be conserved?
Energy and matter together are conserved.
What is temperature?
The measure of the average kinetic energy of the
individual particles of matter.
How do thermometers measure temperature?
When the temperature is warmer, the molecules of the liquid in the thermometer move quicker which causes the liquid to rise. The opposite thing happens when the temperature is colder, the molecules in the liquid slow down and the liquid sinks.
How are the three temperature scales alike? How are they different?
Alike - divided into degrees
Celsius degrees are the same size as Kelvin degrees, but both are larger than Fahrenheit
All have different temperatures for freezing point/melting point of water
What is heat?
Heat is thermal energy moving from a warmer object to a cooler object, AKA energy that's in transit
What is the relationship between thermal energy and temperature? Between thermal energy and heat?
Temperature is one of the factors that determine an object's thermal energy. The other are the number of particles and the arrangement of the particles. Heat is the flow of thermal energy between objects.
What happens to the motion of an object's particles as the object's thermal energy increases? What happens to the temperature of the object?
When the motion of an object's particles increase, its temperature
All else equal, this will result in an increase in the object's thermal energy
Why do some materials get hot more quickly than others?
Some materials are better conductors of thermal energy. For instance metals.
What are conduction, convection, and radiation?
Conduction, convection, and radiation are three ways that heat can be transferred.
Conduction transfers from one particle to another without the movement of matter (contact).
Convection transfers heat by movement of currents within a fluid (liquid or gas).
Radiation transfers energy using electromagnetic waves.
Identify each example of heat transfer as conduction, convection, or radiation: opening the windows in a hot room; a lizard basking in the sun; putting ice on a sprained ankle.
Opening the windows in a hot room - convection
A lizard basking in the sun - radiation
Putting ice on a sprained ankle - conduction
How can heat be transferred across empty space?
It can be transferred through radiation.
In what direction will heat flow between two objects with different temperatures?
Heat flows spontaneously from the warmed object to the colder object (high to low, just like diffusion/osmosis)
How does a glass of lemonade become cold when you put ice in it?
Thermal energy flows from the lemonade to the ice.
What kind of substance conducts thermal energy well?
A conductor transfers thermal energy well. (metal, tile)
Would a copper pipe work better as a conductor or an insulator? Why do you think so?
Metals are normally better conductors and will transfer the heat better than holding it in.
Why are two panes of glass used in the window?
Because air is a good insulator, the trapped air between the panes slows the transfer of heat into and out of the building.
Are electricity and magnetism related? Explain.
Yes. Electric charges that move are the source of magnetic fields.
What is the difference between an insulator and a conductor? Give an example of each.
In thermodynamics: _________________________________________________________________________ Conductor - A material that transfers heat well (ie. Iron, teflon) _______________________ Insulator - A material that does not transfer heat very well. (ie. Air, water) ________ In electrodynamics: ________________________________________________________________________ Conductor - A material that lets electricity pass through (ie. Copper, super-cooled helium) _______________________________________________________________________________________________________ Insulator - A material that does not let electricity pass through (ie. Plastic, ground)
What is an electric circuit?
An electric circuit is an electric current that is maintained when the terminals of a voltage source are connected by a conducting pathway. AKA Electrons going around a closed system
Why does a compass needle move when placed near a wire carrying an electric current?
The electric current produces a magnetic field
What happens to a compass needle when the circuit is turned off?
The needle will align with the magnetic field of the Earth and point back to the magnetic north
How do particles with the same charge interact?
They repel each other (not sure)
How do particles with the opposite charge interact?
They attract each other (not sure)
What is static electricity?
The buildup of charges on an object.
What are the three ways by which static charge is produced?
By rubbing electrons from one material to another (Friction), by letting charges move from a negatively to a positively charged object (Contact/Conduction), or by exerting an external electric force to draw in or repulse electrons from one end of an object to create an unbalance in the charges of the object, but still maintain the net charge (Polarisation/Induction).
How is static electricity discharged?
Static energy is discharged when it comes into contact with an object of opposite charge. At that point, electrons move until both objects have the same charge.
How are electric charges similar to magnetic poles?
Electric charges that are the same repel each other, and electric charges that are different attract each other. Magnetic poles that are the same repel, and magnetic poles that are different attract
How are electric charges different from magnetic poles?
With magnetic poles, there is always a south pole and a north pole. Electric charges, however, can exist alone. A negative charge can exist without a positive charge.
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