DAY 80 - Conservation of Energy
#Goals: SWBAT...
1. ... Memorize and use the potential energy equation
2. ... Apply a problem solving strategy to conservation of energy problems
3. ... solve conservation of energy problems
WARM-UP:
1. A child jumps on a trampoline. Draw bar graphs to show the forms of energy (KE or PEg) present in the following situations.
a. The child is at the highest point.
b. The child is at the lowest point.
2. During a hurricane, a large tree limb, with a mass of 22.0 kg and a height of 13.3 m above the ground, falls on a roof that is 6.0 m above the ground.
a. Ignoring air resistance, find the kinetic energy of the limb when it reaches the roof.
b. What is the speed of the limb when it reaches the roof?
CLASSWORK
1. QUIZ
2. Problem solving with Potential Energy
What is a reference line?
Where do you put the reference line?
If your reference line isn't the same as your classmates, will you have different answers?
Watch the following, and write your answers in your notes: VIDEO
3. Solving Potential Energy Problems
Example Problem #1 pg 290
You practice: start with the warm-up problem, then do pg 291 #6, #7, #4, and #5
4. Lab Setup
If you haven't yet, you'll need to read the lab
Next, view the setup VIDEO
5. Procedure & Data Collection
HOMEWORK
1. Lab Setup Prep
If you haven't yet, you'll need to read the lab
Next, view the setup VIDEO
A. where should the cart be when the weight touches the chair?
B. what is the mass of the weight
C. what will you use distance and time to calculate?
2. pg 306 #33, 34, 54, 63, 66
***Conservation of Energy Labs are now late. Turn them in for partial credit. This was an individual assignment, which means you each need to turn one in...***
CLASSWORK:
0. Review. Last class we:
- watched videos and made bar graphs showing energy transfer
- reviewed and used the problem solving strategy from page 295
- solved a problem together with Mr. P from Flipping Physics
1. HW Questions?
2. Conservation of Mechanical Energy Practice
Solve pg 297 17, 18 & pg 308-309 73-76
Your group will be assigned one problem to show/explain on the board
17: Kevin bottom of valley: 29.7m/s top of hill: 9.90m/s
18: Ramon 1.00m above platform
73: Gerald a. 4.90x103 J b. 4.90x103 J c. 4.90x103 J
74: Mayte a. 2x104 J b. 2x104 J c. 40m/s
75: Elijah a. 42 m/s b. 8.9 x 101 m
76: Sheila 407 J, 2.0 x 101 m/s
3. Collisions.
A. DEMO: What are the types of collisions?
B. Is Momentum Always Conserved?
Let's think... if the system includes the same two cars, before and after a collision, is momentum conserved?
...if the system includes the two cars before the collision, but a third car bumps car #2 after the collision, is momentum
conserved?
C. Is Kinetic Energy Always Conserved?
A. Calculate the KEi and KEf for Case 1, 2, and 3
B. Elastic Collisions
C. Inelastic Collisions
4. Example Collision Problem
In an accident on a slippery road, a compact car with a mass of 575 kg moving at 15.0 m/s smashes into the rear end of a car with mass 1575 kg moving at 5.00 m/s in the same direction.
a. What is the final velocity if the wrecked cars lock together?
b. How much kinetic energy was lost in the collision?
c. What fraction of the original kinetic energy was lost?
5. Practice Problems
Solve pg 300 19, 20
HOMEWORK:
Solve: pg 300 #21
For our last unit, we will study electronics and the circuits you use in your daily lives. Very enlightening... :-)
Watch: https://www.youtube.com/watch?v=-n1pSHzdahc
- Why does the polystyrene (foam) plate keep the "Brainiac" from getting electrocuted?
Read chapter 22, pages 590-594. Answer pg 594 1-2; pg 610 #39
- There may be a short reading quiz... :)