i need help

i need help on my lab report in chimestry please

Lab1: Ball Toss Data Analysis (Physics with Vernier Experiment 6)

Ball Toss

When a juggler tosses a ball straight upward, the ball slows down until it reaches the top of its
path. The ball then speeds up on its way back down. A graph of its velocity vs. time would show
these changes. Is there a mathematical pattern to the changes in velocity? What is the
accompanying pattern to the position vs. time graph? What would the acceleration vs. time graph
look like?

In this experiment, you will use a Motion Detector to collect position, velocity, and acceleration
data for a ball thrown straight upward. Analysis of the graphs of this motion will answer the
questions asked above.

OBJECTIVES

 Collect position, velocity, and acceleration data as a ball travels straight up and down.

 Analyze the position vs. time, velocity vs. time, and acceleration vs. time graphs.

 Determine the best fit equations for the position vs. time and velocity vs. time graphs.

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

MATERIALS

computer Vernier Motion Detector
Vernier computer interface volleyball or basketball
Logger Pro wire basket

PRELIMINARY QUESTIONS

1. Think about the changes in motion a ball will undergo as it travels straight up and down.
Make a sketch of your prediction for the position vs. time graph. Describe in words what this
graph means.

2. Make a sketch of your prediction for the velocity vs. time graph. Describe in words what this
graph means.

3. Make a sketch of your prediction for the acceleration vs. time graph. Describe in words what
this graph means.

PROCEDURE

1. Connect the Vernier Motion Detector to the DIG/SONIC 1 channel of the
interface. If the Motion Detector has a switch, set it to Normal.

2. Place the Motion Detector on the floor and protect it by placing a wire
basket over it.

3. Open the file “06 Ball Toss” from the Physics with Vernier folder.

4. In this step, you will toss the ball straight upward above the Motion Detector and let it fall
back toward the Motion Detector. This step may require some practice. Hold the ball directly
above the Motion Detector. Click to begin data collection. You will notice a clicking

sound from the Motion Detector. Wait one second, then toss the ball straight upward. Be sure
to move your hands out of the way after you release it. A toss of 0.5 m above the Motion
Detector works well. You will get best results if you catch and hold the ball above the
Motion Detector.

https://www.youtube.com/watch?v=2yrIArt0rbU
5. Open the Logger pro file provided in Moodle for Lab 1. Examine the position vs. time

graph. Repeat Step 4 if your position vs. time graph does not show an area of smoothly
changing position. Check with your teacher if you are not sure whether you need to repeat
the data collection.

ANALYSIS

1. Print the three motion graphs. The graphs you have recorded are fairly complex and it is
important to identify different regions of each graph. Click the Examine button, , and
move the mouse across any graph to answer the following questions. Record your answers
directly on the printed or sketched graphs.

a) Identify the region when the ball was being tossed but still in your hands:

 Examine the velocity vs. time graph and identify this region. Label this on the graph.

 Examine the acceleration vs. time graph and identify the same region. Label the graph.

b) Identify the region where the ball is in free fall:

 Label the region on each graph where the ball was in free fall and moving upward.

 Label the region on each graph where the ball was in free fall and moving downward.

c) Determine the position, velocity, and acceleration at specific points.

 On the velocity vs. time graph, decide where the ball had its maximum velocity, just as the
ball was released. Mark the spot and record the value on the graph.

 On the position vs. time graph, locate the maximum height of the ball during free fall. Mark
the spot and record the value on the graph.

 What was the velocity of the ball at the top of its motion?

 What was the acceleration of the ball at the top of its motion?

2. The motion of an object in free fall is modeled by y = v0t + ½ gt

2
, where y is the vertical

position, v0 is the initial velocity, t is time, and g is the acceleration due to gravity (9.8 m/s
2
).

This is a quadratic equation whose graph is a parabola. Your graph of position vs. time
should be parabolic. To fit a quadratic equation to your data, click and drag the mouse across
the portion of the position vs. time graph that is parabolic, highlighting the free-fall portion.

3. Click the Curve Fit button, , select Quadratic fit from the list of models and click .
Examine the fit of the curve to your data and click to return to the main graph.

4. How closely does the coefficient of the t
2
term in the curve fit compare to ½ g? Calculate the

corresponding % error and use the obtained value when you answer this

question.

5. The graph of velocity vs. time should be linear. To fit a line to this data, click and drag the
mouse across the free-fall region of the motion. Click the Linear Fit button, .

6. How closely does the coefficient of the t term in the fit compare to the accepted value for g?
Calculate the corresponding % error and use the obtained value when you answer this

question.

7. The graph of acceleration vs. time should appear to be more or less constant. Click and drag
the mouse across the free-fall section of the motion and click the Statistics button, .

8. How closely does the mean acceleration value compare to the values of g found in Steps 4
and 6? Calculate the corresponding % difference and use the obtained value when you
answer this question.

9. List some reasons why your values for the ball’s acceleration may be different from the
accepted value for g.

NOTE

When the true value of the quantity being measured is considered to be known (e.g. the

acceleration of the free fall at a certain location on Earth), the accuracy of the experiment will be

determined by comparing the experimental result with the known value. This will be done by

calculating the percentage error of your measurement compared to the given known value. If Qexp

stands for the experimental value, and Qref stands for the known value, then the percentage error

is given by:

% Error =
𝑄𝑒𝑥𝑝 − 𝑄𝑟𝑒𝑓

𝑄𝑟𝑒𝑓
× 100%

When a given quantity is measured using two different methods, two different experimental

values, Qexp 1 and Qexp 2. If the true value is not known, the percentage difference between the two

experimental values has to be calculated. The percent difference contains no information about

the accuracy of the experiment; it is just a measure of the precision. The percentage difference

between the two measurements is defined as:

% Difference =
𝑄exp 1 − 𝑄exp 2

𝑄exp 1+𝑄𝑒𝑥𝑝2 /2
× 100%

EXTENSIONS

1. Determine the consistency of your acceleration values and compare your measurement of g
to the accepted value of g. Do this by repeating the ball toss experiment five more times.
Each time, fit a straight line to the free-fall portion of the velocity graph and record the slope
of that line. Average your six slopes to find a final value for your measurement of g. Does the
variation in your six measurements explain any discrepancy between your average value and
the accepted value of g?

2. The ball used in this lab is large enough and light enough that a buoyant force and air
resistance may affect the acceleration. Perform the same curve fitting and statistical analysis
techniques, but this time analyze each half of the motion separately. How do the fitted curves
for the upward motion compare to the downward motion? Explain any differences.

3. Perform the same lab using a beach ball or other very light, large ball. See the questions in #2
above.

4. Use a smaller, more dense ball where buoyant force and air resistance will not be a factor.
Compare the results to your results with the larger, less dense ball.

5. Instead of throwing a ball upward, drop a ball and have it bounce on the ground. (Position the
Motion Detector above the ball.) Predict what the three graphs will look like, then analyze
the resulting graphs using the same techniques as this lab.

6. Repeat your quadratic and linear curve fits to the position graphs but use the time offset
option in the general curve fit dialog. Interpret the constant and linear terms of the quadratic
fit. What do they signify? What are the units of each term?

7. Repeat the linear fit to the velocity graph but use the general curve fit button, . In that
dialog, choose the linear fit and enable the time offset option. Interpret the y-intercept of the
linear fit. What does it signify? What are its units?