Energy Flashcards
What is the universe?
The Universe is everything we can touch, feel, sense, measure or detect.
Types of Energy
Elastic, electrical, thermal, radiation, chemical, wind, sound, hydraulic and nuclear.
What is the universe made of?
Matter and energy
What is elastic energy
Energy stored in an object due to its compression or extension
Elastic energy example
Compressed spring
Stretched elastic
Electrical energy
Energy resulting from the ordered movement of electrons from one atom to another.
Electrical energy example
Power plant
Battery
Generator
Thermal energy
Energy resulting from the random motion of all particles in a substance
Thermal energy example
Fire
Heating element
Sun
Radiation energy
Energy contained in and transported by electromagnetic waves
Radiation energy
Light bulb
Microwave oven
Sun
Cellphone
Radiographic equipment
Fire
Radio
Television
Chemical energy
Energy stored in molecular bonds
Chemical energy example
Apple
Candle wax
Fossil fuels
Wind energy
Energy resulting from the movement of air
Wind energy example
Wind
Hydraulic energy
Energy resulting from the flow of water
Hydraulic energy example
Waterfall
River
Sound energy
Energy contained in and transported by sound waves
Sound energy examples
Sound
Music
Nuclear energy
Energy stored in atomic nuclei
Nuclear energy example
Atomic nuclei
Sun
Energy definition
Energy (E) is the ability to do work or effect change.
This can originate in a multitude of natural phenomena
Energy can be stored as potential energy of different types (see slide 4 & 5). Kinetic energy is energy that is active and happening via motion.
Energy is measure in __
Energy is measured in Joules (J)
1 joule = 1 Newton * 1 meter = 1 N*m
Law of Conservation of Energy
Energy can neither be created nor destroyed; it can only be transferred or transformed.
Transfer of energy
Transfer of energy: energy of the same type is moved from one place/object to another (ex: a billiard ball striking (transferring kinetic energy to) another billiard ball)
Transformation of energy
Transformation of energy: energy changes from one form to another (ex: a light bulb transforms electrical energy into radiation energy)
Energy Efficiency
Useful energy/amount of energy consumed
Useful energy
“Useful” Energy is energy output related to the intentional use of a device
Waste energy
“Waste” Energy is energy output unrelated to the intentional use of a device
What determines useful vs waste energy
“Useful” and “Waste” Energy are determined by the intended use of the device.
Ex: A light bulb can be a source of illumination or heat.
Thermal Energy
measured in Joules; symbol: Ethermal)
Energy contained in a substance determined by the movement and number of particles.
More energy =
more matter
Cold
Low movement, low temperature
Hot
High movement, high temperature
Temperature
Temperature is a measure of particle motion
(measured in degrees; Celcius, Farenheit, Kelvin Symbol: T)
Temperature is not a measure of energy; it measures the average speed/motion of the particles making up matter.
Energy is proportional to motion of particles and quantity of matter
Heat
Heat is the transfer of Thermal Energy
(measured in Joules; symbol: Q)
Heat is the amount of thermal energy gained or lost
Q = ΔEthermal
If ΔEthermal is negative,
thermal energy is lost and temperature is lowered
If ΔEthermal is positive,
thermal energy is gained and temperature is increased
Heat is always transferred from the _____ object to the _____ object.
Heat is always transferred from the hotter object to the colder object. (Coldness is not an energy and is not transferred)
Thermal Energy
(Ethermal)
only +
Energy results from the movement (+ agitation) of particles and the number (quantity) of particles
Not practical to calculate, requires absolute values
UNIT: J
Heat
(Q)
+ or -
The TRANSFER/movement of thermal energy between two substances or two environments
Can be calculated easily, requires relative values
Unit: J
Temperature
(T)
the measure of the agitation (movement) of particles
UNit: oC
Specific Heat Capacity of a substance
Different materials react to heating differently.
Heat capacity is the amount of energy needed to raise the temperature of 1.0 g of material by 1.0 degree C.
An increase in thermal energy will result in an increase in temperature, but will depend on the amount and type of matter.
The same amount of heat transfer could result in an increase of 10oC in one substance, or an increase of 6oC in another substance.
Heat calculations
Using the formula Q = mcΔT, we can calculate the amount of heat gained or lost by a substance undergoing a temperature change.
(positive if the substance gains heat, negative if heat is lost)
Heat Transfer
-Qlost = Qgained
Whichever substance drops in temperature is the substance that LOSES heat. Whichever gains in temperature gains heat.
Gravitational Potential Energy
Objects have gravitational potential energy based on their vertical position relative to a reference position (usually the ground, the lowest point of a swinging trajectory, etc)
This potential energy represents the potential for “action” when the object is released and allowed to fall.
m
m = mass (in kg)
g
g = gravitational acceleration (in m/s2)
h
h = height (in m)
m/s2 or N/kg?
The units that measure acceleration can be represented by m/s2 or N/kg.
These units are equivalent.
c
c = specific heat capacity of substance (J/goC)
Q
Q = heat (J)
DT
ΔT = change in temperature (oC)
(can be positive or negative: ΔT = Tfinal – Tinitial)
Potential energy depends on ________ and ____________
Heavier objects store more potential energy than lighter objects; potential energy depends on mass/weight.
Objects placed vertically higher store more potential energy than those placed vertically lower; potential energy depends on height.
Kinetic Energy
Ek, Kinetic energy is energy of motion.
An easy way to intuit kinetic energy is to imagine the impact of moving objects.
___________ and _______ objects create a larger impact, they have more kinetic energy.
Heavier objects create a larger impact, they have more kinetic energy.
Faster objects create a larger impact, they have more kinetic energy
v
v = speed (m/s)
Converting km/h to m/s:
(km/h) ÷ 3.6 = (m/s)
(m/s) x 3.6 = (km/h)
Kinetic Energy proportions
Kinetic Energy is linearly proportional to mass, but quadratically proportional to speed.
Mechanical Energy
(unit: Joule (J); Symbol: Em; equation: Em = Ep + Ek)
Mechanical Energy is the sum of Kinetic and Potential energy.
This represents the total amount of energy (actual/kinetic and potential) of an object or system.
In a closed system (no energy allowed to enter or leave), the total energy is _______________.
In a closed system (no energy allowed to enter or leave), the total mechanical energy is constant.
Bank account analogy:
Potential energy = savings account
Kinetic energy = checking account
Mechanical energy = total balance
You can move money between your accounts, but the total balance remains constant.
Mechanical energy represents the total energy available
Potential or Kinetic energy may never be greater than mechanical energy.
Diver story
At the top of the diving board structure, the diver has potential energy only.
As the diver allows himself to be pulled by gravity, the potential energy (PE) gradually transforms into kinetic energy (KE)
Once the diver reaches 0 height, all potential energy will have been converted to kinetic energy:
PEi = Ke
Throughout this transformation process, the total mechanical energy always remains the same.
A pendulum continually transforms potential energy into kinetic and vice versa, while conserving the total mechanical energy at all times.
Force
A Force is an action that can change the motion of an object (or deform the object) by pushing or pulling on it.
Motion
Motion is the process in which an object travels in time and space.
Arrowhead
The arrowhead points in the direction the force is applied.
Dotted line
When forces act at an angle, there is often a dotted line to show the horizontal (or vertical) axis. (The direction of travel)
Tail end
The tail end of the arrow is placed at the point of application of the force.
Newton’s second law:
F = ma
F= force (measured in Newtons, N)
m = mass (measured in kg)
a = acceleration (measured in m/s2, or sometimes N/kg)
Acceleration
Acceleration is a change in motion, it is a change in speed over time, (m/s)/s = m/s2.
The same force will have a greater change in motion on a small object compared to a big object
Types of Force
There are many types of force: friction, drag, electromagnetic, gravitational, elastic, etc. All forces can change motion.
Gravitational force
Gravitational force is the attraction of objects on a planet’s surface towards the center of the planet (downwards) (applies to all bodies, not just planets).
Gravitational force is proportional to the mass of the planet, and the distance to the planet’s center of mass (radius of planet if on surface).
-Mass i
-Mass is a scalar measured in kg, is a constant for a given object, does not depend on where it is (in space, on earth, etc, objects maintain their mass). Mass is the quantity of matter in an object.
Weight
-Weight is a vector (Force) measured in N; weight will depend on where the object is (weightless in space, lightweight on the moon, ‘normal’ weight on earth). Weight is the measure of the gravitational force acting on an object.
9.8 m/s2
Gravitational field intensity = gravitational acceleration
