DAY 24
#GOALS:
1. Define "Free-Fall"
2. Solve problems involving free-fall
WARM-UP
Use the following v-t graph to answer the questions below:
1. What is the initial velocity of the object?
2. If acceleration is -9.8m/s2, what will the objects velocity be after one second? Two seconds?
3. A woman driving at a speed of 23 m/s sees a deer on the road ahead and applies the brakes when she is 210 m from the deer. If the deer does not move and the car stops right before it hits the deer, what is the acceleration provided by the car’s brakes?
4. If you were given initial and final velocities and the constant acceleration of an object, and you were asked to find the displacement, what equation would you use?
CLASSWORK
1. NOTES - Free Fall:
Free fall is a special type of acceleration that only occurs when an object falls through the air in Earth's gravitational field. When solving free fall problems, we make the following assumptions.
Air resistance is negligible.
Objects behave as point particles. (think "particle models" from CH 2)
The acceleration of gravity is constant (9.8m/s2)
Principles of Free-fall can be applied for two situations
1. An object, initially at rest, is released (dropped) in the presence of a gravitational field
2. (We will cover this next class) An object is launched upwards, again in the presence of a
gravitational field
2. Demo
Free Fall Videos
- https://www.youtube.com/watch?v=xQ4znShlK5A
Is this ball accelerating? How can you tell?
Want more?
https://www.youtube.com/watch?v=JG0Fie-yZzc
Want to see what this will look like in college?
https://www.youtube.com/watch?v=47rLgSD8Qs0
3. Practice Problems
Individually, complete Pg 74, 42-44 & pg 82 #98
Answers:
42: a. -39m/s b. brick falls 78m
43: a. 39m/s b. brick still falls 78m
44: 8.3m/s
98: -78m/s (neg symbol means downward) b. -313.6m
4. How To: Writing a Procedure
Answers:
42: A: -39 m/s (upward is positive) B: 78 m
43: A: +39 m/s (do
HOMEWORK
pg 75 #49
pg 82 #96, 97, 99
Notes & Answers: https://edpuzzle.com/media/5787ef5da163208e0e742624
CLASSWORK:
Free-Fall Practice Problems:
Pg 75 47-50
D. LAB: How Fast is My Fastball?
Mr Alexander wants to know how fast you can throw an object upwards. Your team will design a lab to calculate the initial velocity of a thrown object. You will choose your materials and your experimental procedure. If you can provide evidence that you threw your object with a faster velocity than Mr Alexander can throw, you will receive extra credit for your team.
Abstract: What is the purpose of this lab?
Materials: What object did you use? What tools did you use to measure with?
Procedure: How did you set up the experiment and how did you take your measurements? Draw the experimental setup, including the path the object took through the air.
Data: Write down your measurements, preferably in a data table.
Calculations: Calculate the initial velocity of the thrown object. Show your work.
Conclusion: How fast did your team throw the object?
HOMEWORK:
pg 75 problem 50
Read 86-89 (reading quiz Fri), pg 89 problems 1-3