The Bird and The Ball

Materials: Computer and School Network

Time Allotment: 3 Class Days

Purpose:

The purpose of this activity is to analyze the motion of an object which travels in a vertical direction. The motion represented in the simulation is the motion of a ball thrown vertically upward with an initial velocity of 80 m/s (up). After 10 seconds, a bird eats the ball.

Procedure:

To begin this lab:

  1. Log on to the student server in the usual manner.
  2. Open the Math/Science folder; then open the Science Apps folder; open the Physics folder.
  3. Once the Physics Explorer-One Body application; chose Open... from the File menu.
  4. A directory dialogue box should appear. Open the Physics 163 folder, the Unit 1 folder, and finally the Bird and the Ball file by double-clicking on its icon.

Upon completing the above procedure, the Physics Explorer application will open up and three separate windows will be displayed on the monitor. The window on the top left (titled Control Panel) will allow the user to control certain aspects of the simulation. The bottom left window (titled Graphical Display) will depict the motion of the ball in graphical form. The right window (titled The Bird & The Ball) will model/simulate the motion of the object.

Running the Simulations:

On the left side of the model/simulation window, there is a panel of tools which are important to the operation of this lab. The top three tools in the panel are Control tools which are used to control the simulation. The top tool is the GO Tool. Clicking once on the GO Tool will run the simulation from the beginning. The second tool in the panel is the STOP Tool. Clicking on the STOP Tool pauses the simulation. Double-clicking on the STOP Tool will reset the simulation to its initial state. The third tool in the panel is the CONTINUE Tool. Clicking on the CONTINUE Tool (which works only if the STOP Tool has been clicked) will allow the simulation to continue from where it left off before being stopped. Try experimenting with these three tools, observing how they are useful in controlling the simulation.

Analyzing the Motion:

Run the simulation and observe the three graphs in the Graphical Display window. Observe the Single Step button in the Control Panel window. Clicking on this button as the simulation is running will step the simulation through its motion one step at a time. Using this feature may slow the motion down and make for better observation. Study the simulation and graphs in order to answer the following questions.

1. A ball undergoes vertical motion and is acted upon only by the force of gravity. Prior to reaching its peak, the ball's

  1. Position is _____________ (increasing, decreasing, remaining constant)
  2. Velocity is _____________ (increasing, decreasing, remaining constant)
  3. Velocity is _____________ (positive, negative, zero)
  4. Acceleration is _____________ (positive, negative, zero)

     

2. A ball undergoes vertical motion and is acted upon only by the force of gravity. At the instant that the ball reaches its peak, the ball's

  1. Velocity is _____________ (increasing, decreasing, remaining constant)
  2. Velocity is _____________ (positive, negative, zero)
  3. Acceleration is _____________ (positive, negative, zero)

     

3. A ball undergoes vertical motion and is acted upon only by the force of gravity. As the ball falls from its peak, the ball's

  1. Position is _____________ (increasing, decreasing, remaining constant)
  2. Velocity is _____________ (increasing, decreasing, remaining constant)
  3. Velocity is _____________ (positive, negative, zero)
  4. Acceleration is _____________ (positive, negative, zero)

     

4. In the Control Panel window, there is a pop-up menu titled Vector Display. Currently the No Vector option is selected from this pop-up menu. Depress the mouse on the No Vector option to see other options in this pop-up menu. Move the mouse vertically down until the Velocity (V) option is selected. See the diagram at the right. Then let up on the mouse. Run the simulation and observe the size and direction of the velocity vector during the simulation.

  1. As a ball undergoes vertical motion and is acted upon only by the force of gravity, the velocity of the ball is ______________ (always changing, usually changing, always constant).

     

  2. An object with changing velocity is said to be __________________.

 

5. Use the Vector Display pop-up menu in the Control Panel window to select the Acceleration (A) option. Repeat the directions in step 4 if unsure of how to do this. Run the simulation and observe the size and direction of the acceleration vector during the simulation.

  1. Can an object travel upwards and still have a downwards (negative) acceleration? If so, then explain what the downwards (negative) acceleration means.

     

     

  2. Describe the acceleration of an object (constant or changing, direction, magnitude) which undergoes vertical motion and is acted upon only by the force of gravity.

     

     

  3. A ticker tape trace of the motion of the ball is shown to the right. If this simulation was run in a world in which falling objects fell at constant speed, what would the ticker tape look like? Draw it next to the diagram on the right.

 

 

6. The graphical description of this simulation is shown at the right.

  1. Place a big dot on the curve in each graph at the time when the ball reached its peak. Note that prior to this time, the ball is rising and after this time the ball is falling.

     

  2. Indicate the following for the peak:

    v = __________ m/s

    a = __________ m/s2

  3. Use the velocity-time graph to calculate the distance the ball rises (i.e., the maximum altitude). PSYW

     

     

     

  4. Use the velocity-time graph to calculate the distance the ball falls. PSYW

     

  5. Use the answers to the above two questions to calculate the altitude of the ball when the bird eats it. PSYW

     

 

Extensions:

1. Consider a ball thrown vertically upward with a velocity of 50 m/sec.

  1. Sketch the velocity-time and acceleration-time graphs for the motion of the ball during the first seven seconds. On each graph, provide markings for the vertical axes.

  2. Use the velocity-time graph to calculate the ball's altitude after seven seconds. PSYW

     

  3. Use the velocity-time graph to calculate the distance that the ball travels during the third second. PSYW

 

 

2. Luke Autbeloe throws a ball downward with a speed of 20 m/s from the top of a very tall bridge. The ball strikes the river below three seconds later.

  1. Sketch the velocity-time and acceleration-time graphs for the motion of the ball during these three seconds. On each graph, provide markings for the vertical axes.

  2. Use the velocity-time graph to calculate the distance which the ball traveled in the first second. PSYW

     

  3. Use the velocity-time graph to calculate the distance that the ball travels during all three seconds. PSYW

 

Conclusion:

Use several well-written and complete sentences to explain how the different features (slope and shape) of postion-time and velocity-time graphs are revealing of the qualities of an object's motion. Be specific and provide an exhaustive explanation. Do a bang-up job!

 

 

 

 

 

 


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This page created by Tom Henderson and last updated on 11/16/98.