do now 1. how do we find total mechanical energy? 2. a 3 kg soccer ball is travelling at 15 m/s when...
TRANSCRIPT
Do Now
1. How do we find total mechanical energy?
2. A 3 kg soccer ball is travelling at 15 m/s
when it is 9 m above the ground.
A. What is its kinetic energy?
B. What is its potential energy?
3. What does the law of conservation of
energy state?
Today’s Agenda
5 min
•Do Now
5 min
• Important Dates40 min
•Energy Review10 min
•Practice Test
Today’s Agenda
5 min
•Do Now
5 min
• Important Dates40 min
•Energy Review10 min
•Practice Test
Important Dates & Reminders Final Exam Next Thursday!
Tutoring during advisory or after school most days!
Monthly News Project Due on next Tuesday
Photography Project Due Friday, May 4th
Extra Credit Opportunities US Space and Rocket Center Thank You Letter
Due Monday, May 7th Extra Monthly News Project
Due Friday, May 4th
Today’s Agenda
5 min
•Do Now
5 min
• Important Dates40 min
•Energy Review10 min
•Practice Test
TME is the sum of all kinetic and potential energy.
Total Mechanical Energy
Total Mechanical Energy GraphsPotential energy is plotted with the total mechanical energy on the graph below. What does the graph of kinetic energy look like?
Position (m)
En
erg
y
(J)
Total mechanical energy
PE
Position (m)
En
erg
y
(J)
Total mechanical energy
PE
KE
KE
½ Total
½ Total
Example
A 40-kg skydiver has a speed of 25 m/s when he is 300 m above the ground. What types of energy does he have? Calculate the values for both types of
energy. Calculate total mechanical energy.
Student-Guided Example
A 2 kg soccer ball has a speed of 15 m/s when it is 10 m above the ground. What types of energy does it have? Calculate the values for both types of
energy. Calculate total mechanical energy.
Think-Pair-Share
A 0.5 kg paper airplane has a speed of 4 m/s when it is 3 m above the ground. What types of energy does it have? Calculate the values for both types of
energy. Calculate total mechanical energy.
Complete the three independent practice problems on the Daily Organizer.
Independent Practice
Energy cannot be created or destroyed. Energy can only be transferred from one form to another but the total amount never changes!
Law of Conservation of Energy
Law of Conservation of Energy
The sum of KE and PE remains constant. One type of energy changes into another type.
For the falling book, the PE of the book changed into KE as it fell.
As a ball rolls up a hill, KE is changed into PE.
PEI + KEI = PEF + KEF
Kinetic and potential energy convert to one another
KE max KE max
no PE no PE
PE maxno KE
PE max
no KE
Example
A 4 kg crate is dropped from the top of a 20 m tall ledge and falls to the ground. What was its initial potential energy? What was its initial kinetic energy? What was its final potential energy? What was its final kinetic energy?
Student-Guided Example
A 7 kg crate is dropped from the top of a 40 m tall ledge and falls to the ground. What is its initial potential energy? What is its initial kinetic energy? What is its final potential energy? What is its final kinetic energy? What is its final speed?
Think-Pair-Share
A 40 kg skydiver drops from an airplane, which is 1500 m high in the air. What is the kinetic energy of the skydiver when he gets to the ground? Find the initial potential energy. Find the initial kinetic energy. Find the final potential energy. Find the final kinetic energy. Find the final speed of the diver.
Tag Team Problems
Tag Team 1
A 3 kg bowling ball is dropped from a building that is 10 m tall. How fast is the ball going right before it hits the ground? Partner 1: Find the initial potential energy
and the final kinetic energy. Partner 2: Find the final speed. Partner 3: Check their work
Tag Team 2
A 0.7 kg book falls from the top of a shelf that is 3.5 m tall. How fast is the book going right before it hits the ground? Partner 1: Find the initial potential energy
and the final kinetic energy. Partner 2: Find the final speed. Partner 3: Check their work
Multiple Choice Problem
Law of Conservation of Energy
A 2 kg crate is dropped from the top of a 40 m tall ledge and falls to the ground. What is its speed when it hits the ground?A. 28 m/sB. 40 m/s C. 80 m/sD. 784 m/s
Law of Conservation of Energy
A 2 kg crate is dropped from the top of a 40 m tall ledge and falls to the ground. What is its speed when it hits the ground?A. 28 m/sB. 40 m/s C. 80 m/sD. 784 m/s
Complete the three independent practice problems on your Daily Organizer.
Independent Practice
Independent Practice Problems 1. A 1 kg plate was at rest on a tabletop
1.5 m above the ground before falling to the ground. What was its speed right before it hits the ground?
2. A 0.5 kg rock is dropped from a cliff 70 meters high. What is its speed right before it hits the ground?
3. A 0.25 kg apple falls from a tree that is 16 m tall. What is the speed of the apple right before it hits the ground?
Silently and independently complete the provided exit ticket. When you are finished, work on the homework (practice test).
Exit Ticket
Today’s Agenda
5 min
•Do Now
5 min
• Important Dates40 min
•Energy Review10 min
•Practice Test
You have the next 10 minutes to silently and independently work on the practice test that is due Friday.
Feel free to ask questions during this time!
Practice Test