Kinetic Energy
What is the formula for kinetic energy?
1/2*m*v^2
What is the formula for gravitational potential energy?
Mass*Gravity (9.81)*Height
What is work?
What is the formula for thermal energy? Units?
Q=m*Δ T*Cp Joules
What is the difference between thermal energy and temperature?
Thermal energy is the total thermal kinetic energy, temperature is the average
Calculate the kinetic energy of a car that is moving at 9.2m/s and has a mass of 1000kg.
1/2*1000kg*(9.2m/s)^2
42,320J
Define potential energy
Stored energy that has the 'potential' to become kinetic energy
What is the formula for power? Units?
P=Work/Time Watts
Calculate Q
mass=20kg
20C to 40C
cp=2000(J/kg*C)
20kg*20C*2000(J*kg/C)=800,000J
Define the following words:
Conductor
Insulator
Radiation
Conductor-something that allows thermal energy movement
Insulator- something that slows thermal energy transfer
Radiation-thermal energy conduction through space (campfire)
Define Kinetic Energy
Energy in motion
Name the 3 types of potential energy
Gravitational PE
Chemical PE
Elastic PE
Calculate the work done for a man that pushed a box with 400N of force for 4m.
1600J
I have a piece of steel. Steel has a specific heat of 400J/kg*c. You heat a 30kg chunk from 23C to 44C. Find the thermal energy
Q=252,000J
How much work is someone doing if they are pushing with 1000N of force against a wall?
0J, the wall is not moving
Calculate the kinetic energy of a truck that has a mass of 2391.44kg and has a velocity of 22.73m/s
1/2*2391.44kg*(22.73m/s)^2=617,772.21J
Calculate the PE of a rock that has a mass of 90kg that sits atop a 100m cliff
90kg*9.81m/s/s*100m=88,290J
What is AMA? What about IMA?
Actual Mechanical Advantage and Implied Mechanical Advantage. AMA-the number of times your force is multiplied. IMA-in a perfect world the number of times your force is multiplied
I have a glass of water. Water has a specific heat of 4000J/kg*c. You heat a 15.5kg section from 26C to 34C. Find the thermal energy
When we learned about simple machines, why can a machine never have an efficiency of higher than 100%?
You cannot create energy
I have a toy car that has a mass of 75g. Calculate the kinetic energy if the car is moving at 4m/s
75g to kg=0.075kg
1/2*0.075kg*(4m/s)^2=0.6J
Calculate the PE of a 450g toy truck that falls off a 350cm tall table
450g to kg=0.45kg
350cm to m=3.5m
0.45kg*9.81m/s/s*3.5m=15.45J
Calculate the work and power
A man pushed a 500N box with a force of 350N. He pushed this box 5m and it took him 4 seconds.
W=350N*5m=1750J
Power=1750J/4s=437.5W
Find the specific heat of aluminum if the temperature rose from 30C to 45C and it took 96,000J of energy. The block has a mass of 8kg.
cp=800J/kg*c
96000J=8kg*15C*cp
96000J=120*cp
800J/kg*c=cp
What is happening at the subatomic level when something is hot vs cold?
When something is hot, the particles vibrate quickly. When something is cold, they vibrate slowly