RFE 2001.06.19.001
New applet that lets you steer a changing velocity vector by controlling an acceleration vector in an acceleration dial.
url: Acceleration/Basic Facts/Simulate It/Accel. vs. Veloc.url: Velocity/Basic Facts/Explain It
This applet will be located at Acceleration/Basic Facts/Simulate It/Accel. vs. Veloc. Another instance of it, somewhat reduced in size vertically, will be at Acceleration/Basic Facts/Explain It, pages 5 to 7.
The applet is very similar to the applet under Velocity that lets you control a car's motion by dragging a velocity vector in a velocity dial. Here, the car is replaced by a velocity vector and the velocity dial by an acceleration dial. There is no analogue of the speedometer and compass on he right-hand side of the applet screen in Acceleration Space.
The portions of the applet window are titled 'Velocity Space' on the left and 'Acceleration Space' on the right. Acceleration Space contains only an acceleration dial in the middle of this space. Velocity Space contains a very short pair of axes at the center to mark the origin of velocity space and a velocity vector whose tail end is attached to this origin. The tip of the vector can be dragged to any point in Velocity Space, but not beyond. The entire vector cannot be dragged, i.e., its tail end remains attached to the fixed origin at the center.
As soon as one clicks in the acceleration dial, an acceleration vector is drawn and the tip of the velocity vector starts moving in a direction and at a rate as dictated by the acceleration vector. The motion is frozen when the tip of the velocity vector reaches the boundary of Velocity Space or when the mouse button is released. At this point, the tip of the velocity vector can be dragged to some other point, and the motion can be resumed by clicking at some point in the acceleration dial.
If one clicks in the acceleration dial right in the center, with a bit of an error margin, one sets the acceleration to zero and one gets a constant velocity. There should be a display somewhere in Acceleration Space that the acceleration is zero, or unequal to zero, whatever the case may be.
There is a trace toggle button. When that is selected, the trace of the velocity vector's tip will be shown, as in One-Ball the trace of the ball is shown. Clicking the button again will hide the trace.
There is a REPLAY button. This becomes active only after the velocity vector has been moved around. When the button is clicked, the initial velocity vector selected by the user before clicking in the acceleration dial will be restored and the initial acceleration vector will be attached with its tail end to the tip of the velocity vector. A forward STEP button becomes active at this point as well. This button lets you step through the recorded motion of the velocity vector in steps of reasonable and fixed size. At every step, the acceleration vector will be shown attached to the tip of the velocity vector. It will also be shown in its acceleration dial. The trace may be on or off during the stepping process. After the first step, a back-step button will become active as well that lets you step backward. See the Work-Kinetic Energy applet in this connection.
There is a RESET button that resets everything to the default.
There is a toggle button labeled 'Object'. When this button is selected, a disk is placed on the screen. This disk is in Position Space which one should imagine as being superimposed on both Velocity Space and Acceleration Space. Thus, the disk can move freely on top of both of these spaces. It should have a transparent appearance if that is possible, so that any vectors or boundary lines that it may happen to cover will still be visible through the disk. The disk can be dragged by hand to any point in Velocity or Acceleration Space. When the acceleration has been set and the velocity vector is responding, the disk moves accordingly representing the corresponding position. See the Work-Kinetic Energy applet in this connection. When the acceleration is zero, the disk will be the only thing moving on the screen. When the disk crashes into a boundary, the motion is frozen. It will resume when the disk is either dragged away from the boundary or the velocity vector is reset to point to the inside of the boundary.
The disk's motion will continue when the 'Object' button is unselected. Selecting it again will show where the disk is at that moment. Since one has taken the mouse off the acceleration dial to select this button, one will have to restart the motion by clicking in this dial.
When one is in REPLAY mode and the object is selected, the acceleration vector will be shown attached to the object. It is also shown attached to the velocity vector in this mode. The attached acceleration vector will make it clear that the acceleration vector never points to the outside of the object's path.
(2001.06.19) Hans Laue
RFE/BUG 2001.07.25.001 There are two items to be done in the Energy Race, one alteration and one bug fix.
url: Energy/Energy Conservation/Simulate It/Energy RaceBUG: In its default setting, the applet displays the message "Turn Friction Off" on both buttons underneath the two inclines. Since the friction is already set to zero, the buttons should display the message "Turn Friction On". After one has toggled the buttons, the buttons perform correctly.
ALTERATION: During the race, the colored blocks are randomly transformed from blue to red and pink. Change this so that, for each of the two systems, only the blocks on the left are transformed into red TK blocks (starting with the block in the top left corner, going down the first column, then continuing at the top of the second column, etc.), and only the blocks on the right are transformed into pink RK blocks (starting with the block in the bottom right corner, going up the last column, continuing at the bottom of the second last column, etc.) The blue blocks in the middle are gradually being transformed. This way, it is easier to see what is going on and the colors in the system correspond to the three colors underneath the system box.
(2001.07.25) Hans Laue
RFE 2001.07.18.001
Add another button labeled 'Show Position Vector' that toggles with 'Hide Position Vector', like the 'Show Axes'/'Hide Axes' that is already there. A position vector gets drawn when 'Show Position Vector' is selected. The default state of the applet does not show the position vector.
url: Position/Position Vector/Explain It
Power Back to Top
url: content/power
Reference Frame Back to Top
url: content/refframe
Simple Harmonic Motion Back to Top
url: content/shm
Speed Back to Top
url: content/speed
State Qul? Back to Top
url: content/statequl
Time Back to Top
url: content/time
Torque Back to Top
url: content/torque
Vectors Back to Top
url: content/vectors
Velocity Back to Top
url: content/velocity
RFE 2001.06.17.001
New applet that lets you steer the motion of a car (or generic object like a disk) by controlling a velocity vector in a velocity dial.
url: Velocity/Basic Facts/Explain ItThis is an applet that takes up the full content screen width, but less than the full content screen height, to leave some room for text underneath the applet. The applet will go on pages 2 and 4 of the content item above, with the text on those pages underneath the applet. Pages 1, 3, and 5 will have only text in the content area.
The applet area is divided by a vertical line into two areas: the area on the left is titled "Position Space" and the area on the right "Velocity Space". Position space could be somewhat wider than velocity space.
The controls include a button that toggles between the picture of a race car and a flat disk (orange?). The car is the default on p.2. It is placed in the center of position space and can be dragged to a new location.
Velocity space contains a circle (velocity dial) in its lower half and a speedometer (needle moving across a horizontal scale) and direction indicator (compass dial with unit vector rotatable around fixed point at center). The default setting has the velocity vector equal to zero.
The object in position space and the velocity vector in the velocity dial in velocity space are both draggable. When the object is being dragged, this is just to set the position of the object. There will be no effect on the velocity vector in the dial.
When one clicks anywhere in the velocity dial, the system draws a velocity vector from the center of the dial to this point and the object moves with this velocity. If one releases the mouse button, the motion is frozen. Clicking again somewhere else in the velocity dial, will resume the motion with the new velocity. Not releasing the mouse button and dragging the velocity vector with the mouse will continually update the object's velocity and move the object accordingly. The speedometer and compass always correspond to what is shown in the velocity dial. If the object is a car, the car's image always points in the direction of the car's velocity. If the object hits the boundary of position space, the motion is frozen and will resume only if the velocity is changed to a value that moves the car to the inside of position space. Alternately, one could drag the object and then get the motion going again by clicking in the velocity dial. While one is dragging the object, the velocity vector in the dial responds accordingly.
There is a trace button that allows the object's trace to be displayed. There is a REPLAY button and a STEP button that work together as follows. After having moved the object, either by dragging the object itself or by dragging the velocity vector, one can click REPLAY which, in the first place, will restore the object to its initial position. If one then clicks STEP repeatedly, the object will retrace its path in steps and the corresponding velocity vector in the dial will be shown at each step. IN ADDITION, the velocity vector will be superimposed on the object at each step. Already upon clicking REPLAY, the initial velocity vector that started the motion will be superimposed on the object. The programming done in the Energy/Work-Kinetic/Explain applet may be useful here. The step size should be reasonably large (and fixed), and the program will have to store position readings at much shorter time intervals in order to be able to calculate good instantaneous velocities to display at each step. The trace could be on or off during this stepping process. If it is on, it should be apparent that the instantaneous velocity vectors are tangential to the trace. One should be able to step forward and backward along the object's path, as in the Wk-Kin applet. When one has taken at least one step, in the REPLAY mode, a back-step button will become active to allow stepping back.
There should be a RESET button that restores the applet to its default setting.
(2001.06.17) Hans Laue
BUG 2001.07.18.001
(a) There are two columns of text in the applet window. The right column must be shifted left somewhat so that the 'm/s' unit of the last average velocity item comes into view.
(b) When one clicks in the applet window, the ball is positioned at that spot. The clock does not start running until one moves the ball. Change this so that the clock starts running as soon as one clicks in the window, even if the ball does not get dragged.
url: Velocity/Average/Explain It
Adjustment (b) is needed so that one can simulate the situation in which an object has zero velocity for a while, then non-zero velocity, then again zero velocity. With this one can show that the average velocity is not equal to the mean of the initial and final velocity.
(2001.07.18) Hans Laue
Work Back to Top
url: content/work