This animation shows a cube moving about a
three dimensional space. It presents ** two dimensional
projections** of this motion into several planes. Please see
notes below.

The purpose of this animation is to visualize
several slices or projections of three dimensional projectile motion.
These projections show that the object accelerates ** only**
in the planes that are

First, the xyz axes: The xyz axes form
a ** three dimensional coordinate system** that has
three axes: the

When you first load this page and before you make any changes to the animation....

- The
is the*x-axis*. It runs from -60 on the left to +60 on the right.*red horizontal line* - The
is the*y-axis*. It runs from -60 on the bottom to +60 at the top.*green vertical line* - The
is the*z-axis*that you are looking straight down. It looks like a blue dot because you can not see its length. You will need to rotate the xyz axes to see its length. Imagine this axis as coming out of and going into the screen. It runs from -60 behind the screen to +60 in front of the screen.*blue line*

The spinning buttons: The animation
can be spun in various ways with the ** 'Theta'** and

Also note the ** gray bounding box**. The

Two other buttons: The **
'Rho'** buttons move the xyz axes

What you can see: The **
middle column of checkboxes** control the visibility of several
aspects of the animation. More about these a bit further down the page;
however, basically:

- The
checkbox shows or hides the bouncing cube.*'Cube'* - The
,*'XY Plane'*, and*'XZ Plane'*checkboxes show or hide their respective planes.*'YZ Plane'* - The
,*'XY Shadow'*, and*'XZ Shadow'*checkboxes show or hide the projection of the cube's motion onto their respective planes.*'YZ Shadow'*

About the planes and shadows: This
animation shows motion in a ** three dimensional space**.
It is interesting to see

This animation lets you see three slices of the ** (x, y, z)
space**. It lets you see the

Hopefully, this animation helps you see how just a ** part
of the motion** can be examined while other parts of the motion
are temporarily ignored. It's often handy to see a three dimensional motion
considering only two of the axes. If you activate the (x, y) plane and the
(x, y) shadow, for example, then you will see the projection of the cube on
to the (x, y) plane. It will look pretty much like a flat square moving
around.

About the acceleration buttons: You
can consider these to control the ** direction** in which

The central ideas to this animation: The cube is moving with projectile motion in a three dimensional space. The acceleration due to gravity can be 'turned on' in any of six directions, or it can be completely 'turned off'.

The acceleration makes the path, or trajectory, of the cube to be curved. It's trajectory is a parabola. This curved path, however, is only mapped out, or shadowed, in the planes that contain the axis along which gravity is pulling.

Within the plane that does not contain the acceleration axis, or direction, the motion is not curved. No parabola there. It's straight line motion.

For example, at startup the acceleration due to gravity is aimed in the
negative y-direction. We often liken this to 'downward' in most diagrams.
The cube bounces around in a curved three dimensional path. But if you click
on the ** (x, z)** plane and shadow, and

Well, there are two other planes to look at. If you examine the motion of
the ** shadow** in both the (x, y) and (y, z) planes
you will see that the shadow is moving along a

Try making the gravity work ** 'sideways'** or

Try turning gravity ** 'off'**. You should see
straight line motions for all of the projections since there would be zero
net force on the cube.