is a beta 1.1c version of the HitModeler Weather program, and you are invited
to participate in the beta testing. If you find errors in the program or
would like to suggest improvements, please send an e-mail to Thomas.J.Benson@nasa.gov.
With this software you can investigate how a
baseball flies through the air
by changing the values of the factors
that affect the aerodynamic forces on the ball.
These are the same forces that generate the drag
of an aircraft wing. The
is determined by the initial velocity and the relative
size of the drag and weight of the ball. We provide a
page of results which you can use to check your
There are several different versions of the HitModeler software that are now available.
This page contains the weather version, a simplified version of
HitModeler intended for younger students to learn the basics.
All input to this version of the program is made using buttons.
The motion is two dimensional and you can study the trajectory of the ball
with selected weather conditions.
This page contains instructions on the use of the buttons in the program.
For experienced users, we have a
web page that contains only the software.
There is a more complex
of HitModeler that has the same functionality as the weather version
but you control the input to the program by using
input boxes and sliders.
You can download the weather version of the program to your computer
by clicking on this yellow button:
With the downloaded version, you can run the program off-line and do not
have to be connected to the Internet.
This program is designed to be interactive, so you have to work with the
All input for this version of the program is made with buttons.
To operate a button, use your mouse to move the cursor over the button, then
left click on the mouse to "push" the button.
The current values of variables are presented to you in boxes.
A black box with cyan numbers are inputs to the program which are set
by the selected buttons.
A white box with
black numbers is an output box and the value is computed by the program.
If you see only a grey box at the top of this page, be sure that Java is
enabled in your browser. If Java is enabled, and you are using the Windows XP
operating system, you need to get a newer version of Java. Go to this link:
try the "Download It Now" button, and then select "Yes" when the download box from Sun
The program screen is divided into two parts:
At the top of the screen is the graphics window.
The graphics window shows the
of the hit ball.
The simulation is two dimensional and you are looking parallel to the ground.
are the only forces acting on the ball.
Along the top of the window, the height and distance from the
plate are updated during the flight. There is a wall set at
375 feet from home plate.
The ball is launched at 100 mph at 45 dergees to the horizon.
At the bottom of the screen are the values of the inputs to the
program and the input buttons.
The active button is shown in yellow.
The default conditions are an Average Day
with no wind and a default
The average day is based on an NASA model of the
atmosphere and how the pressure and temperature change with
You change the temperature, the atmospheric
pressure, and the relative humidity of
the air by using the appropriate button.
The program then calculates the air density
that affects the drag on the ball.
You can set the wind at your back (+ Wind) or wind in your face (- Wind)
and can change the drag coefficient to zero by using the buttons at the right.
When you have your conditions set, click on the yellow SWING
button at the top to launch the ball into the air.
You can save your flight trajectory to compare with a new set of
conditions by pushing the blue Save button. And you can
clear all of the graphics by pushing the orange Clear button.