What is Energy?
What is energy?
The ability to do work or cause something to change
energy that is stored is called:
potential energy
What is kinetic energy? Give an example of ONE Form
Kinetic energy = motion energy
Examples = light, electricity, mechanical / motion, thermal energy, etc.
Calculate the potential energy of a 20kg bag of potatoes sitting 3m off the ground. Use 9.8 m/s/s as gravity.
20kg * 3m * 9.8m/s/s = 588J
Describe the STATE and FORM of energy that I begin with, and what I end with
Batteries are in a flashlight -> I turn on the flashlight
Start = chemical potential
End = radiant / light / electrical kinetic
When you do work on an object some of your energy is _______________ to that object
transferred
The type of potential energy that can increase based on an object's location (ie if I lift a ball higher, it has more energy to fall with)
Gravitational potential energy
This type of energy is STORED when I bend, twist, or move an object away from its original state.
(hint: springs use this type of energy)
Elastic potential energy
Calculate the KE of a 1200kg car travelling at 30m/s.
KE = 1/2 * 1200kg * 30m/s^2 = 540000J
I have an apple -> I eat the apple and ride my bike
Start = chemical potential
End = mechanical kinetic
What are the two variables that gravitational potential energy can be calculated with? What units do we measure each in?
Mass (kg) and height (meters)
List the units used to measure the following:
- Energy
- Velocity (or speed)
Energy = JOULES
Velocity/speed = M/S or meters per second
Describe thermal energy. How does conduction use thermal energy?
Thermal energy = motion of particles vibrating inside of a substance
Conduction = direct contact between source and receiver of heat
Calculate the total energy of a rollercoaster whose carts weigh 1300kg and has a drop of 200m.
PE = TE = 1300kg * 9.8m/s/s * 200m = 2548000J
An atom sitting in a power plant's reaction chamber -> the atom is split and releases enough heat to boil water
Start = nuclear potential
End = thermal kinetic
Define the two states of energy.
Potential - storing energy with the ability to use it later
Kinetic - anything in motion
The acronym MELTS stands for what? What STATE of energy does this acronym describe?
Mechanical
Electrical
Light / radiant
Thermal
Sound
It's for kinetic energy
Describe how radiation transfers energy, and provide on real world example.
Energy moves through an empty space
Example = the sun, space heaters, a fire
I calculate that the potential energy of a skater going down a ramp from its highest point is 1200J. What is the skater's TE? What is the skater's KE at the bottom of the ramp?
TE = roughly 1200J
KE at the bottom = 1200J
What energy transformation takes place when a radio is plugged in and turned on?
Electrical to sound
Describe the law of conservation of energy, and give an example.
Energy cannot be created or destroyed
Example: total energy never changing on a rollercoaster
Imagine I drop an egg from 4.5m off the ground, giving it a potential energy of 200J. What is my KE right before my egg hits the ground? How do you know?
Should be around 200J
Law of Conservation of Energy: energy is not created or destroyed (some is lost to drag/air resistance)
Define convection, and use it to describe the motion of molecules inside of water that is boiling. You can also use convection currents in the mantle for your answer.
YOUR ANSWER MUST INCLUDE DENSITY!!
Convection is transfer of energy between molecules through a liquid (like air or water)
Water (or currents in the mantle) get hot, become less dense, rise, cool off, become more dense, and fall.
Calculate the velocity of a 5kg ball rolling on the ground with 200J of KE. Don't forget correct units in your answer!
V = Square root 2*200J / 5kg = 8.94m/s
Electrical -> radiant -> thermal