Types of Energy/Transformations
What type of energy is stored in a spring?
Elastic potential energy
True or False: energy can be created and/or destroyed
FALSE
Does kinetic energy increase or decrease as an object slows down?
KE decreases
True or False: GPE and the height off the ground are directly proportional.
True
What are 3 examples of objects that store EPE? Be specific about the situations the objects are in!
A compressed/stretched spring, a stretched rubber band, a bent pole...
Name as many different types of energy as you can, go!
Elastic potential energy, kinetic energy, gravitational potential energy, chemical potential energy, thermal energy, light energy....
Aang tells Toph that the boulder that she sent skidding across the ground can’t have conserved energy because it slowed down. Explain to Aang why he is incorrect.
Aang is incorrect because he is forgetting that the boulder is not in a closed system, so we can’t ignore the effects of friction. The kinetic energy of the boulder did not disappear, it just turned into heat energy because of the frictional force.
Does a change in velocity or a change in mass have a higher impact on KE?
Velocity
What has more GPE: an airplane that is 5,000 m off the ground, or a bird flying next to the airplane? (P.S.- that bird can fly really high!)
Airplane
What are the units for the spring constant k?
N/m
How do you find the total energy of an object?
Add up all the different types of energy!
A 100 kg roller coaster cart has 120,000 J of GPE and 5,000 J of KE on a frictionless track. How much KE does it have when it reaches h = 0 m?
KE = 125,000 J
True or False: the KE of an object depends on which direction it’s moving
False
How much GPE does an 8 kg cat have if it’s sitting on a roof 3 m off the ground?
GPE = 235.2 J
Spring 1 has k=100 N/m and spring 2 has k=150 N/m. Which spring is stronger?
Spring 2
Describe how energy transforms when a ball is thrown straight up into the air.
The KE of the ball’s motion turns to GPE as it climbs higher. At the peak of the ball’s path it has only GPE, which is then converted back to KE when it falls and picks up speed
A 100 kg roller coaster cart has 120,000 J of GPE and 5,000 J of KE at some point on a frictionless track. How much GPE does it have when it is moving at a velocity of 20 m/s?
GPE = 105,000 J
How much KE does an 8 kg cat have if it stalks a bird moving at 0.5 m/s?
1 J
If the height an object is at doubles, what happens to its GPE?
GPE also doubles
A spring with k=300 N/m is compressed by 10 cm = 0.1 m. How much EPE does it store?
EPE = 1.5 J
If you decrease your speed by half, by what factor does your KE decrease?
What happens to the EPE stored in a spring if you double the distance that you stretch it?
EPE quadruples (is multiplied by 4)