Home Cooking 10/24/14 - Discussing Gravitational Acceleration and a Whole Bunch of Physics Stuff

Video:

(thank you to Yusuf for featuring and helping in this video)

Results: 

(thanks LoggerPro)

Analysis:

I found a similar lab online that involved rolling a tennis ball down a ramp and across a table. Rather than critiquing their video, I constructed my own with the intention of simply discussing what is going on considering all the good stuff (acceleration, gravity, etc) that is featured in this short video. First, lets discuss

Gravity: Denoting by the symbol g, gravity is the force of an object towards Earth. Though it changes slightly depending on altitude, it is usually known is 9.8 m/s/s/. Does this m/s/s/ look familiar? Yes! M/s/s/ indicates acceleration and 9.8 m/s/s/ is the acceleration of free falling objects! In this video, gravity is acting upon the ball as it travels down the ramp. 

     Side topic - Air Resistance: Air resistance involves the forces moving against an object as it falls. The larger the surface area of an object, the more air resistance it encounters and therefore the slower it falls. 

Acceleration: First off, acceleration is a vector quantity, as it relates to the velocity of an object (which also deals with direction). In this video, we are witnessing positive acceleration due to gravity. As discussed previously, a free falling object has an acceleration of 9.8 m/s/s downward due to gravity on Earth. Positive acceleration is when an object has an acceleration in the same direction of its velocity, which is depicted in this video. Constant acceleration is when an object's velocity changes by the same amount each second. For example, after 1 second an object has a velocity of 4 m/s and, after 2 seconds, it has a velocity of 8 m/s. 

Surface Friction (New Idea!): In the section of the video we can't see, the ball continues moving across the table and slows down (negative acceleration!). So why does this happen? Surface friction has a part in this by opposing the motion of the ball as it attempts to cross the table. Eventually, the ball will stop. 

Picket Fence and Ball Drop Labs - Accuracy vs. Precision

Picket Fence Free Fall

Objective: Measure the acceleration of a freely falling body (g) using a Picket Fence and a Photo-gate. 

Preliminary Discussion:

If an object is moving with constant acceleration, the shape of its velocity vs. time graph is a quadratic curve. The acceleration of the picket fence will be the same as the initial velocity, whether you are dropping or throwing downwards. 

Procedure:

1. Fasten the Photo-gate to the stand and provide a soft surface for the picket fence to land on. 

2. Connect the Photo-gate to the Lab Analysis app

3. When ready, begin to collect data and drop the picket fence from the top of the Photo-gate. 

4. Repeat this step multiple times to fill out data table

5. Examine your graphs and the slope of your graphs. 

Data Graphs: 

Data Discussion:

It is hard to determine the exact value we should be looking for not knowing our exact value of gravity in our classroom. This lab's procedure was efficient and involved few errors. Since the gate was held steadily by the stand, there was little error when it came to accidental movement. 

Ball Drop 

Objectives: 

- Collect position, acceleration, and velocity and analyze the graphs of each.

- Determine the best fit for the graph data collected

- Determine the mean acceleration from the acceleration vs. time graph 

Preliminary Discussion:

Predictions:

1. Positive vs. Time

2. Velocity vs. Time

3. Acceleration vs. Time 

Procedure:

1. Connect the motion detector to the Logger Pro App.

2. Place the motion detector on the floor.

3. Toss the ball straight up above the motion detector and let it fall back down. Record the data while it is doing this. Be sure to move your hand out of the way after you release it. 

4. Examine your graphs.

Data Graphs: 

Data Discussion:

This lab was quite difficult to manage in terms of reducing error. The motion detector was on the floor and could have quite possibly picked up movement from its surroundings. There was no way of determining where to start/how high the ball would go and that most likely affected our data.

OVERALL ANALYSIS;

The goal of these two labs was to determine which method was more accurate/precise in finding the value of gravity, which is about 9.8 m/s/s.Of course, this process involves the presence of errors, leading us to discuss: which lab has fewer errors? After reviewing data from both the Picket Fence and Ball Drop lab, I have come to the conclusion that the Picket Fence lab is a better method of reaching the 9.8 m/s/s. The Picket Fence lab involved dropping the picket fence through a photo gate that is held steadily in place by a stand. Since all we have to do was drop the picket fence through the gate, there was very little error. The Ball Drop lab involved throwing a ball up above the motion detector. This lab has multiple systemic errors. The motion detector has to be placed on the floor and would pick up movement from the surroundings. Also, the motion detector would pick up the motion of our hands as we threw the ball up. When it comes to the ball itself, it was started at/thrown to different distances throughout the lab, affecting the data of the lab. 

CONCLUSION:

Both labs involved creative procedures and electronically gathered information. Though neither are more accurate than the other, the Picket Fence procedure/lab has less major errors than the Ball Drop lab due to its better procedure/materials. 

Video Analysis of Motion: Open Inquiry

Constant Velocity

Velocity - the rate of change of an objects position 

Constant velocity - an object covers the same distance per second. The magnitude and direction remain constant. 

Example: car moving at constant speed 

Constant Accelerated Motion

Acceleration - a vector quantity that is defined as the rate at which an object changes it's velocity 

Constant acceleration - velocity is changing at a constant rate each second 

Example: free falling object 

Original Videos

Motion On An Incline

Objectives: 

Terms:

Motion - motion is a change in position of an object in terms of times and revenge point

Motion includes displacement, direction, velocity, acceleration, and time.

Slope - the steepness of a line or altitude. 

Displacement - the overall change in the position of an object 

Velocity - is a vector measurement of the rate and direction of the change in the position of an object.

Materials: 

- Vernier data-collection interface

- Cart

- Lab Quest Device and App

- Motion Detector 

- Track, elevated by box

- Vernier dynamics track

Procedure: 

1. Connect a motion detector to the Lab Quest.

2. Position the motion detector at the end of the track

3. Elevate the track opposite the motion detector

4. Hold the car 20 cm from the motion detector and zero it

5. Begin collecting data and launch the car up the track. Be sure to stop the car. 

6. Compare and label the position vs. time and velocity vs. time graphs

7. Label the car rolling freely up the ramp, the farthest point, and the car moving freely down the ramp on the position vs. time graph 

8. On the app, ultitilize the slope instead of the tangent tool

Data Results 

Position Result : 

Prediction : 

Velocity Result : 

Data Analysis

1. The graphs depicted represent position vs. time and velocity vs. time graphs. 

2. Both graphs depict the car being pushed up the track, 

3. We discovered we can find the tangent by selecting a section of the graph and utilizing the slope (m= -a/b)

4. The highest point, or fartherest point, is depicted by the peaks on the graphs. 

5. Velocity can have a positive or negative value