# Acceleration of Gravity

 Materials: Computer and School Network Time Allotment: 3 Class Days

### Purpose:

The purpose of this activity is to use sample data to determine the acceleration of gravity on an imaginary planet and to extend the concept of the acceleration of gravity to other motion concepts.

### Analysis:

The following analysis questions are critical to your success on this activity. It is not recommended that you continue unless your understand the answers to these questions.

1. Construct a free-body diagram for a free-falling 0.2-kg mass (200 g) and a 1.0-kg mass (1000 g). Show the type, direction, and magnitude of the force(s) acting upon the mass.

2. Calculate the net force and the acceleration of each mass above. PSYW
 m = 0.2 kg m = 1.0 kg
3. If velocity-time data for a free-falling mass were collected and subsequently plotted, then what would you expect the graph to look like? Sketch your prediction in the graph at the right and justify your answer in the space below.

4. Explain how the velocity-time data plot could be used to determine the acceleration of the free-falling object.

### Procedure:

Part A - Determination of the Acceleration of Gravity on Krypton

1. Two objects of different mass are dropped from rest on the planet Krypton. Velocity-time data (experimental) for the two objects are shown below. Use the Graphical Analysis program to construct a velocity-time plot for each individual data set. Activate the regression line and statistics options using the Graph menu (refer to your graphical analysis manual if necessary). Print the two plots with the statistics showing. Include the printouts with your lab report when you submit it to the teacher.

2. Use the two graphs to write an equation (in slope-intercept form) which appropriately identifies the relationship between the velocity and the time for each of the individual data sets.

 m = 5.0 kg m = 20.0 kg

3. What does the slope of each of the velocity-time graphs represent? Explain.

4. Determine the acceleration of gravity on the planet Krypton. Explain your answer.

5. Does the acceleration of gravity seem to depend upon the mass? Justify your answer by making explicit reference to the data and graphs which you have just analyzed.

Part B - Extension of the Acceleration of Gravity Principle

1. Determine the weight of a 5-kg and a 20-kg object on the planet Krypton.

 5.0 kg 20.0 kg

2. A 5-kg object is dropped from the top of a Superman Towers on the planet Krypton. It strikes the ground 14.0 seconds later. Determine the...
1. ...speed of the object when it reaches the ground. PSYW

2. ...height of the Towers. PSYW

3. Michael Jordan and Mr. Schmidgall periodically play basketball on the planet Krypton. One day, scientists analyzed MJ's vertical jump, collected velocity-time data and constructed the following plot. Use the plot to answer the following questions.

1. Mark the point on the graph (with a big dot) that represents the instant in time at which Michael Jordan is at the peak of his trajectory.
2. Determine the height to which MJ can jump on the planet Krypton. PSYW

3. If scientists were to construct a plot of Mr. Schmidgall's vertical jump, how would it be different? Sketch what you would predict it to look like and explain your answer.

4. Use your own prediction to determine Mr. Schmidgall's jump height. PSYW

5. In the space below, sketch position-time plots for both Michael Jordan's and Mr. Schmidgall's jumping motion on the planet Krypton. Place both plots on the same graph and label the plots as "MJ" and "Mr. S."

### Data:

Experimental velocity-time data for the free-fall of a 5-kg and a 20-kg object on the planet Krypton:

### Conclusion:

Define the acceleration of gravity, identify at least one variable which effects (and at least one which doesn't effect) the acceleration of gravity, and explain in detail why all objects experience the same acceleration of gravity regardless of their mass.