Make a Stopwatch - DIY with GeoGebra

Uploaded by GeoGebraChannel on 29.01.2011

We are going to make a stopwatch from a clock face. The important things that you need to
have are a center point, a top point and a circle. You do not actually have to label
this around. You need a center point, a top point and a circle. You can draw that using
the center/point tool. Now, how to make this into a stopwatch. Get
the slider tool and we are going to make an angle slider over here. So we are going to
click, select angle. It automatically goes to alpha from 0 to 360. Now how many seconds
are there in 360 degrees. Sixty. So we need our increment to be 360/60 or 6 degrees.
The other things should be alright. Click slider. This is good. A little narrow. Click
animation. I think we should reduce the speed to 0.5 to make it a little bit slower. This
is important. It needs to be increasing. The wheel needs to be turning in an increasing
direction. So we have that and we click Apply. Use our move tool. We want a point here that
is alpha degrees along from the top point. (That is why we needed the top point.) So
what we need is “angle of given size”. Click on the little arrow and look for “angle
of given size”. We click on our top point, our middle point and we tell it that we want
it to go clockwise – that is important – and then we do not want it to be fixed
at 45. We want it to take on the value of alpha. So we mark it and click on alpha. So
“alpha” and “clockwise”. OK. And – ok the new point is sitting right
on 2 so we cannot see it. So let us move it off of 2. Get the move tool and move alpha.
Ok. This is what? 7 seconds or something. Now we need a clock hand or pointer. We need
a pointer. So we are going to use a vector for a pointer just because it has an arrow
on the end. So go to the line tool. Vector and then click
on center point to our new point. And then we don’t really want to see that angle,
so right-click and deselect Show object. We really want this to be nice and thick so we
can see it, so we are going to right-click, Object properties. Go to Style and make it
thick and some kind of color. OK. Now, how we do animate this. We go up to the
slider. We right-click and chose “animation on”. There it goes. Now that looks a little
fast on my machine. So I would probably get a clock from somewhere with a second hand,
stop the animation at 12. I am going to stop it now and then take my move tool and wind
it all the way back to 12. Time how long it takes to go all the way around, i.e. one minute.
This is probably too fast and divide the speed by that number.
Right-click on the slider. Go to Object properties and reduce the speed. Now I usually just try
this until it works. And you can try that. And so probably – let us say 0.15. Let us
see. Looks a little slow. Actually it looks pretty good. OK. That’s how to do it.