Sahagun 2 Truths and 1 Lie
Potential and Kinetic Energy
WORK
Energy Conservation Concepts
Energy Conservation Math
Energy Transformations and Transfers
Final Jeopardy
100
1) I am in a YouTube video with over 100 million views
2) I helped design a demonstration at the Exploratorium
3) I have caught a home run at a Giants game
2) I helped design a demonstration at the Exploratorium
100
1) Energy of motion:
2) Energy due to position
1) Kinetic
2) Potential
100
1) Formula for work:
2) Units of work (and abbreviation):
1)Force x Distance
2)joules (J)
100
The roller coaster is at rest at point A. AFTER point A, it is in motion. Zero-point is at the bottom of the structure. There is no friction.
Where is KE the GREATEST?
D (lowest point on the track)
100
The "shortcut" formula for calculating velocity of an object dropped from a specific height.
√2gh
(square root of 2gh)
100
What energy transformation occurs when you slide your phone on the desk and it stops?
( ___________ --> ___________ )
Kinetic Energy --> Thermal Energy
200
1) I once hiked all 213 miles of the John Muir trail
2) I don’t drink coffee
3) I recently finished getting a Master’s Degree in Statistics
1) I once hiked all 213 miles of the John Muir trail
200
The sum of potential and kinetic energies in a system.
MECHANICAL Energy
200
WAS WORK DONE? (Put a Y or N for each one)
1) Lifting your friend up from the floor
2) Carrying your friend across the room
3) Pushing your friend across the floor
1) Y
2) N
3) Y
200
The roller coaster is at rest at point A. AFTER point A, it is in motion. Zero-point is at the bottom of the structure. There is no friction.
At what point(s) does the roller coaster have both P.E. and K.E.?
B, C, D, E
200
A skydiver jumps from a plane. They start with 392,000J of potential energy. (assume no friction or air resistance)
How much K.E. will the skydiver have 3/4 of the way down?
294,000J
(If the skydiver has fallen 3/4 of the way down, then they have lost 3/4 of their P.E. which has transformed into K.E. 3/4 x 392,000J = 294,000J)
200
Turning on a fan
( _______________ --> _______________ )
electric energy transforms into kinetic energy of turning fan blades
300
1) My dog is a trained scent-finder
2) I have never gone camping
3) I was in a car that caught on fire
1) My dog is a trained scent-finder
300
The velocity of a car changes by 3x
By how many times does its KE change by?
9x
300
15J of work is done to move a large 10kg box across the floor of the classroom.
How much did its K.E. change during this process?
15J
The CHANGE in Kinetic Energy of the object is EQUAL to the work done.
300
The roller coaster is at rest at point A. AFTER point A, it is in motion. Zero-point is at the bottom of the structure.
If the coaster system has 100,000J of total energy at A, how much total energy does the system have at E?
A) Less than 100,000J
B) 100,000J
C) More than 100,000J
100,000 J
300
A human with a mass of 90kg jumps off a diving platform that is 5m above the water.
What is their velocity at the moment of impact with the water?
(Round to the nearest TENTH)
9.9m/s
300
A pendulum WITH friction and air resistance.
(________ --> ________ & ________ )
GPE --> KE and Thermal Energy
400
1) Senior year, I was the oldest student in my high school
2) Freshman year in high school, I was 5'4"
3) Freshman year in high school, I played a varsity sport
3) Freshman year in high school, I played a varsity sport
400
A bird flies from an altitude of 100 to 500 feet.
By how many times does its Potential Energy change? (?x)
(Think carefully!)
5x
400
A 800kg car slams on its brakes, stopping in 10m. The force from the brakes is 4,000N.
How much work was done on the car? (in the backward direction)
40,000J
400
A ball is on top of a 1m shelf. At what height will it have an EQUAL amount of PE and KE once it falls?
0.5m (halfway down!)
400
The electromagnetic ring launcher launches a ring 1.4m up into the air. If the ring's mass is 33g, how much electric potential energy was used to fire the ring? (assume no friction or air resistance)
0.45J
The ring has 0.033kg x 9.8m/s2 x 1.4m = 0.45J of GPE at the maximum height of its flight. This energy had to originally come from the electric potential energy that it took to fire it.
400
Colliding metal spheres into paper
( _______________ --> _______________ & _______________)
Kinetic energy --> thermal energy & acoustic energy (sound)
400
FINAL JEOPARDY!
You may wager as little as zero (0) or as much as your current score!
Choose wisely! If you get the question wrong, you will lose the amount that you bet!
LET'S GO! FINAL JEOPARDY!
500
1) I am an avid skier
2) I have gray hair
3) I can touch my nose with my tongue
1) I am an avid skier
500
A 2kg model airplane is flying at a height of 3 meters, moving at 5m/s.
How much MECHANICAL energy does it have?
25J of KE, 58.8J of PE
Total Mechanical Energy: 83.8J
500
A 10kg box is lifted up 20m by a crane.
How much work was done on the box?
1960 J
(work = Fd and Fgrav = mg, so... work = mgd)
500
At what point in an object's fall does KE become GREATER than PE?
When the ball is more than half way down to the ground.
500
The electromagnetic ring launcher launches a ring 1.4m up into the air. The ring's mass is 33g. How FAST was the ring moving just before it hit the ground? (assume no friction or air resistance)
About 5.24m/s
The ring has 0.033kg x 9.8m/s2 x 1.4m = 0.45J of GPE at the maximum height of its flight. This will all transform into KE on the way down, with all it being KE just before impact.
0.45J = 1/2mv2 . Solving for v, you get 5.24m/s
500
A battery causes a fan to turn.
( ________ --> ________ --> Kinetic Energy of the fan blade)
Chemical PE --> Electricity (in wires) --> Kinetic Energy of moving fan blade
500
A 60kg skater is atop a 6m hill. What is the maximum amount of work that friction could do for the skater to still make it to the top of the second hill (4m)?
-1,176J of work!
The skater starts with 3,528J at 6m of height. They need 2,352J of kinetic to be able to reach a height of 4m (60kg x 9.8m/s2 x 4m = 2,352J). If they start with 3,528J, and only need 2,352J, then the difference, -1,176J, could be "lost" as thermal energy.