GPE and KE Calculations
A 5 kg brick is being held 2 m above ground. What is the GPE of the brick? Assume we are on Earth. Must include the label.
GPE = mgh
GPE = (5kg)(9.8m/s2)(2m)
GPE = 98 Joules
What does mechanical advantage compare?
Output force to input force
The warmth you feel from rubbing your hands together is what kind of energy?
Thermal Energy
Fill in the blanks to complete the energy transformation:
_______________________ --> _________________
Rubbing your hands together The warmth you feel
Mechanical --> Thermal
What law states that all energy in the universe remains constant?
The Law of Conservation of Energy
A toy car with a mass of 2 kg is moving at a speed of 3m/s. What is the car's kinetic energy? Must include the label.
KE = 1/2 mv2
KE = 1/2(2kg)(3m/s)2
KE = 9 Joules
What percent can efficiency never exceed?
100%
A slingshot utilizes this kind of potential energy.
Elastic Potential
Fill in the blanks to complete the energy transformation:
_______________ ----> __________________
Plug in a lightbulb Light from the lightbulb
Electrical --> Radiant
15 Joules
A 10 kg weight that is lifted 2 meters off the ground, has a potential energy of 196 Joules. If the weight is dropped, how much Kinetic energy should it have on impact with the ground?
According to the Law of Conservation of Energy, nearly all GPE will all be transformed into KE, so...
196 Joules of Kinetic Energy
A pair of scissors is 2 levers, 2 wedges, and 1 screw. What kind of machine is a pair of scissors?
Complex/Compound Machine (2 or more simple machines)
Your phones, computers, lightbulbs, and the sun all have this type of energy in common.
Radiant Energy
(half points if you put thermal)
Provide the 3 main energy transformations that occur in a car engine.
Chemical (from fuel), Thermal (ignition of fuel), Mechanical (engine revs and car moves)
Why would two objects of identical masses have different kinetic energies?
One is moving faster.
KE = 1/2 mv2
A catapult launches a 6 kg rock 20 meters. If the rock was in the air for 5 seconds, how much kinetic energy did it have when it hit the ground?
KE = 1/2(6kg)(4m/s)2
KE = 48 Joules
For mechanical advantage to be greater than 1, what is true about output force compared to input force?
Output force must be greater than input force.
Mechanical Energy
In a pendulum system, all of the GPE turns into kinetic energy. Why does all of the kinetic energy not turn back into GPE?
I am looking for 2 things in your answer for full points
Some is transformed into thermal energy via friction.
(half points for mentioning thermal energy, half for mentioning friction)
What are 3 energy transformations that occur in a growing strawberries for consumption.
If a car on the highway accelerates from 40 km/hr to 80 km/hr, by how many times does it's kinetic energy increase?
Increases x 4
KE = 1/2 mv2
The speed doubles
KE = 1/2 m(2v2) = 1/2m4v2
What are the 3 ways a machine can change how work is done?
Increase Speed
Increase Force
Change the direction of force
What kind of energy is produced in large quantities during the fission (splitting) of an atom?
Nuclear Energy
Name 5 energy transformations that would occur while driving an electric car during winter at night time.
100 points per answer. Any missed transformations are open to steal by other teams
Chemical (battery) --> Electrical (powers all car functions) --> Mechanical (driving the car) --> Thermal (heat during winter) --> Radiant (headlights)
Why would two objects of the same mass and same height above ground have different GPE's?
They are on different planets.
(GPE = mgh, g would have to be different)