In this lesson we extend our knowledge of Uniformly Accelerated Motion to include freely falling objects. We talk about what Free-Fall means, how to work with it and how to identify and object in Free-Fall. Today I get to introduce so many of my fa...vorites: the medicine ball, the vacuum that you can breathe and, of course, little g.
Content Times:
0:22 An Example of An Object in Free-Fall
0:54 Textbook definition of a freely falling object
1:11 We have not defined a "Force" so this is how we define Free-Fall
2:07 No Air Resistance (The Vacuum that You Can Breathe!)
3:10 What does it mean to be in Free-Fall? (The Acceleration due to Gravity)
4:41 The Acceleration due to Gravity - Not on Earth
5:24 g is not constant on Earth. Very close, but not quite
5:56 Common Misconception: Objects moving upward can be freely falling
6:35 Free-Fall is Uniformly Accelerated Motion
7:27 What does the negative mean in -9.81 m/s^2?
7:57 Is "g" positive or negative?
9:01 How can "g" be not constant and we can use UAM?
10:03 Does mass effect the acceleration due to gravity?
10:47 The Review
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Previous Video: Reviewing One Dimensional Motion with the Table of Friends
Next Video: Apollo 15 Feather and Hammer Drop[more]

An advanced free-fall acceleration problem involving 2 parts and 2 objects. Problem: You are wearing your rocket pack (total mass = 75 kg) that accelerates you upward at a constant 10.5 m/s^2. While preparing to take pictures of the beautiful view,... you drop your camera 5.0 seconds after liftoff. 5.0 seconds after you drop the camera, (a) what is the camera's velocity and (b) how far are you from the camera?
Content Times:
0:17 Reading the problem
1:26 Understanding the problem using a picture
2:10 Listing every known variable
3:22 Which part do we start solving first?
3:47 What do we solve for in part 1?
4:46 That's a lot of subscripts, why?
5:24 Starting to solve the problem. Finding the final velocity for part 1.
6:32 Solving for the final velocity for part 2 for the camera
7:46 Why is the final velocity for part 2 for the camera positive?
9:10 Finding the displacement for part 2 for the camera
9:55 Finding the displacement for part 2 for you
10:42 Finding the distance between you and the camera at the very end
11:27 The Review
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Previous Video:
Dropping Dictionaries Doesn't Defy Gravity, Duh![more]

This video continues a problem we already solved involving dropping a ball from 2.0 meters. Now we determine how to draw the position, velocity and acceleration as functions of time graphs.
Content Times:
0:17 Reviewing the previous lesson
1:00 A...cceleration as a function of time
1:31 Velocity as a function of time
2:39 Position as a function of time
3:56 The Review
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Next Video:
Throwing a Ball up to 2.0 Meters & Proving the Velocity at the Top is Zero
Previous Video:
Dropping a Ball from 2.0 Meters - An Introductory Free-Fall Acceleration Problem[more]

This video is an example problem that walks through finding the average speed for the last 2 laps of the 4 lap qualifier for the Indianapolis 500 assuming an average velocity for the first 2 laps. It is actually more difficult than it initially appe...ars.
Content Times:
0:36 Reading the Problem
1:06 Translating to Physics
3:25 A Visual representation of our Known Values
4:07 Beginning to Solve the Problem
5:27 Finding the Time for Part 1
7:15 Finding the Total Time
9:00 Finding the Time for Part 2
10:15 Finding the Average Speed for Part 2
10:45 A Common Mistake
12:07 The Answer
13:15 A Question about Significant Digits
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Next Video:
Introduction to Acceleration with Prius Brake Slamming Example Problem
Previous Video:
Example Problem: Velocity and Speed are Different[more]

We need to know the initial velocity of a projectile leaving the Nerd-A-Pult. That means we need the initial speed and the initial angle. This video shows exactly how I measured both.
Content Times:
0:30 Taking measurements to determine the laun...ch angle
2:02 Defining the angles
3:35 Determining the launch angle
4:38 Using the frame rate to find the change in time
5:08 Measuring the distance travelled during the first frame
6:12 Why initial speed and not initial velocity?
6:39 Determining the average launch speed
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Next Problem: Nerd-A-Pult #2 – Another Projectile Motion Problem
Previous Problem: Nerd-A-Pult - An Introductory Projectile Motion Problem
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Apollo 15 Video Courtesy of NASA: The 1971 Feather and Hammer Drop Experiment performed by Astronaut David Scott. We analyze the experiment to determine the height from which the feather and hammer were dropped. It is a great, basic, introductory f...ree-fall problem.
Content Times:
0:19 Why the experiment was done.
0:32 Let's enjoy the video
1:27 Beginning to analyze the video
2:23 Using the Frame Rate
3:00 Counting the frames
3:50 Solving for the initial height
4:51 The answer to how high the feather and hammer were dropped
5:31 The Review
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Previous Video:
Introduction to Free-Fall and the Acceleration due to Gravity
Next Video:
Dropping a Ball from 2.0 Meters - An Introductory Free-Fall Acceleration Problem
Permissions:
Picture of Moon: By Jmpicot (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Picture of Astronaut David Scott and Apollo 15 video: This file is in the public domain because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted".[more]

In this introductory free-fall acceleration problem we analyze a video of a medicine ball being dropped to determine the final velocity and the time in free-fall. Included are three common mistakes students make. "Why include mistakes?" you might a...sk. Well, it is important to understand what happens when you make mistakes so that you can recognize them in the future. There is also brief description of "parallax" and how it affects what you see in the video compared to reality.
Content Times:
0:26 Reading and viewing the problem
0:50 Describing the parallax issue
1:52 Translating the problem to physics
2:05 1st common mistake: Velocity final is not zero
3:09 Finding the 3rd UAM variable, initial velocity
3:56 Don't we need to know the mass of the medicine ball?
4:35 Solving for the final velocity in the y direction: part (a)
5:39 Identifying our 2nd common mistake: Square root of a negative number?
7:56 Solving for the change in time: part (b)
8:28 Identifying our 3rd common mistake: Negative time?
9:36 Please don't write negative down!
10:27 Does reality match the physics?
11:07 The Review
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Next Video: Graphing the Drop of a Ball from 2.0 Meters - An Introductory Free-Fall Acceleration Problem
Previous Video: Analyzing the Apollo 15 Feather and Hammer Drop -- A Basic Introductory Free-Fall Problem[more]

Video Proof of the Mass Independence of the Acceleration due to Gravity and a little dancing.
Content Times:
0:14 Reviewing the mass independence of free-fall acceleration.
0:56 1 book
1:36 What's a boom box?
2:07 All 4 videos together
2:31 We... can dance if we want to
3:25 Thank you very much for learning with me today
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Next Video:
Don't Drop Your Camera 5.0 Seconds After Liftoff
Previous Video:
A Free-Fall Problem That You Must Split Into Two Parts
Picture Permissions:
Boom Box - By Jmpicot (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons[more]

Again with the graphs? Yes. Absolutely Yes. Graphs are such an important part of any science, especially physics. The more you work with graphs, the more you will understand them. Here we combine graphs and uniformly accelerated motion. Enjoy.
...
Content Times:
0:29 Reading the Problem
1:02 How do we know it is UAM from the graph?
1:26 Two different, equivalent equations for acceleration
2:41 Finding acceleration
3:23 Graphing acceleration vs. time
3:44 The general shape of the position vs. time graph
4:53 Determining specific points on the position vs. time graph
6:06 Graphing position vs. time
6:58 The Review
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Previous Video: Understanding Instantaneous and Average Velocity using a Graph
Next Video: Reviewing One Dimensional Motion with the Table of Friends[more]

Yes, there are mistakes that many people make when it comes to free-fall acceleration problems. I dispel many misconceptions and explain both why people think they are true and why they actually aren't. Oh, and there are some special effects too!
... Content Times:
0:14 Review of the Basics of Free-Fall
1:04 1st Misconception - The acceleration on the way up is positive
2:09 2nd Misconception - The initial velocity going upward is zero
2:45 3rd Misconception - A thrown ball will accelerate faster than a dropped ball
4:00 Reminder - Velocity at the top is zero
4:29 4th Misconception - The acceleration at the top is zero
6:36 Review
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Previous Video:
Creating a Position vs. Time Graph using Stop Motion Photography
Next Video:
A Free-Fall Problem That You Must Split Into Two Parts[more]

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