Unit 7 Concepts 1-4 Study Guide
Explain the difference between the 3 types of thermal energy transfer. Include an example of each.
1. Conduction - transfer of energy through matter by direct contact of particles - Ex. touching a stove and being burned. 2. Convection - transfer of energy by the movement of heated particles - Ex. boiling water 3. transfer of energy through electromagnetic waves - Ex. getting sun burned
Draw a picture of a pendulum or someone hitting a golf ball, showing how GPE, KE, and ME change throughout the object's motion. Make your labels very clear.
Attached in Google Classroom
How high is a 0.5 kg squirrel sitting if it has 36 J of energy?
GPE = ham 36 = 0.5(9.8)(h) 36 = 4.9h 36/4.9 = h h = 7.35 m
What is the energy of a 4 kg apple that is sitting on a 2 m high tree branch?
GPE = ham GPE = 2(9.8)(4) GPE = 78.4 J
What is the energy of a baby who weighs 20 N sitting in a high chair 1.5 m high?
GPE = ham GPE = 20(1.5) GPE = 30 J
Describe how thermal energy flows when a person is sitting in a chair at their desk.
Thermal energy always flows from higher temperature objects to lower temperature objects.
energy
the ability to cause change.
specific heat
the amount of heat needed to raise the temperature of 1 kg of a material by 1 °C or K.
power
the amount of work done in a certain time; the rate at which work is done.
thermal energy
the sum of kinetic and potential energy of the particles in an object.
mechanical energy
the total amount of kinetic and potential energy in a system.
heat
the transfer of energy from one object to another.
work
the transfer of energy that occurs when a force makes an object move.
temperature
a measure of the average kinetic energy of particles in an object.
Determine the energy conversion for the following: a. Light bulb b. Firework c. Flute d. Leaf
a. electrical to light b. chemical to light, thermal, and sound c. kinetic to sound d. solar to chemical
List examples of materials that would classify as conductors vs. insulators.
conductors - metals and skin insulators - air, wood, and plastic
Law of Conservation of Energy
energy can never be created or destroyed, it can only change forms.
kinetic energy
energy in motion
gravitational potential energy
energy stored in objects that are above Earth's surface
Electromagnetic energy
form of energy that is reflected or emitted in the form of electrical and magnetic waves that can travel through space.
conductor
materials that allow heat to flow easily
insulator
materials that do not allow heat to flow easily
potential energy
stored energy
Explain the relationship between temperature and kinetic energy.
temperature is a measure of the average kinetic energy of particles in an object while KE is the amount of energy in motion at an exact point.
Explain the differences between the 3 types of potential energy.
Elastic Potential Energy - energy stored in objects being compressed or stretched. Chemical Potential Energy - energy stored in chemical bonds of compounds. Gravitational Potential Energy - energy stored in objects that are above Earth's surface.
What is the relationship between kinetic and potential energy of a falling object?
In a falling object, GPE converts to KE as the object falls.
What is the kinetic energy of a bike with a mass of 16 kg traveling at 4 m/s?
KE = 1/2 mv^2 KE = 1/2 (16)(4)^2 KE = 8(16) KE = 128 J
How much power is used if a force of 90 N is used to push a box a distance of 30 m in 10 s?
P = W/t P = (90(30))/10 P = 2,700/10 P = 270 J/s
A 10 kg rock falls from a height of 18 m and lands on a guy about 3 s later. How much power did it hit him with?
P = W/t P = (98(18))/3 P = 1,764/3 P = 588 J/s
How much heat is needed to warm 0.072 kg of gold from 20°C to 90°C if the specific heat of gold is 136 J/kg/°C?
Q = mc(Tf - Ti) Q = 0.072(136)(90 - 20) Q = 0.072(136)(70) Q = 685.44 J
Give an example of where you would find each of the following types of energy: radiant, thermal, electrical, sound, nuclear, and electromagnetic.
Radiant - sun and lightbulbs Thermal - fire Electrical - outlet Sound - headphones Nuclear - nuclear power plants electromagnetic - cell phone
150 J of work was done to lift a crate with a force of 20 N. How far was the crate lifted?
W = Fd 150 = 20(d) 150/20 = d d = 7.5 m
A go-cart and rider have a mass of 100 kg. If the cart accelerates at 5 m/s2 during a 25 m sprint, how much work did the cart do?
W = Fd W = (100(5))(25) W = 500(25) W = 12,500 J
A force of 85 N is used to push a box along the floor a distance of 15 m. How much work was done?
W = Fd W = 85(15) W = 1,275 J
Explain why there is no such thing as "cold".
When you feel cold, you are simply feeling the absence of heat.
