Instructions
This page is designed to get you started using the applet. The applet should be open. The step-by-step instructions on this page are to be done in the applet. You may need to toggle back and forth between instructions and applet if your screen space is limited.
Setting the Ball's Initial Position and
Velocity
Setting
a Target and Measuring Point Coordinates
Click the Reset button Click on the ball and drag it to the initial position
(x,y) = (20.0, 10.0) m, as shown in Figure 1 below.
You may find this easier to do if you display the grid by pressing
the Grid toggle button It also helps to adjust one coordinate at a time. Drag the
ball to x = 20.0 m without worrying about the
y-coordinate. Then, hold down the Shift key while dragging
the ball. Now the ball will move only vertically and it will be
much easier to adjust its initial y-coordinate to 10.0 m.
The x-coordinate will remain unchanged while the Shift key
is held down.
Figure 1 Notice the shadow balls on the x and y axes.
They move with the ball and are projections of the ball onto the
two axes. Their positions represent the ball's x and
y coordinates.
The ball's x and y position coordinates are
displayed in the top right corner of the applet. These will be
updated throughout the motion, along with the value t of
the time elapsed. Time elapsed is measured from the beginning of
the motion. Thus, at the beginning of the motion, t =
0. The magenta arrow represents the ball's initial velocity.
(During the motion it represents the ball's velocity at a given
instant.) Adjust the initial velocity to a magnitude of 20 m/s and
to a direction that forms an angle q
with the positive x-axis equal to 60o. Do this
by typing these values in the first column of the velocity data
panel, shown at the bottom of Figure 1, and then press the ENTER
key on the keyboard.
Notice how the display of the x and y components
of the ball's velocity is automatically adjusted to
vx = 10.0 m/s and vy = 17.3
m/s. You can enter values in any of the four velocity data
fields. When you press ENTER, the values in the four fields are
adjusted automatically so that they are consistent. The last
value entered and its partner in the same column are not
adjusted.
You can adjust the initial velocity also by dragging the tip of
the velocity vector. The four velocity data fields will be
adjusted accordingly.
.
. (The
grid is not shown in Figure 1.)