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### Re: It's About Time C

Posted: March 23rd, 2010, 12:32 pm
those sound really easy.... the last one i'm pretty sure i have in my binder near the front. the other stuff i could do even in my head if i REALLY had to (the seconds in a week wouldn't be very fun)

### Re: It's About Time C

Posted: March 23rd, 2010, 4:07 pm
those sound really easy.... the last one i'm pretty sure i have in my binder near the front. the other stuff i could do even in my head if i REALLY had to (the seconds in a week wouldn't be very fun)
have you done this event yet!?!?
they may sound easy but they are much more difficult
for ex.-
How many time zones are used in the U.S.? (one of the easier ones, don't forget about territoreis)

What is a modified Julian date?

What timezone do they use in the international space station?

and many other harder questions I cant remember right now

### Re: It's About Time C

Posted: March 23rd, 2010, 7:43 pm
Has anyone considered making a pendulum that moves in the path of a cycloid? My calculus book says it is a good idea.

### Re: It's About Time C

Posted: March 24th, 2010, 4:18 pm
For people that have been using rigid rod pendulums, what were your masses of the the pendulum and rod? I was trying out a rigid rod and it doesn't seem to last more that a 100 seconds.

My rod is 20 g while the mass I'm using is 250 g. Is weight of the rod the issue or the contact b/w the rod and axle? I'm using a single ball bearing (3/8 in inner diameter, 5/8 in outer diameter) to put them together fyi.

Any help would be appreciated.

### Re: It's About Time C

Posted: March 24th, 2010, 5:10 pm
i've never made a pendulum, but if you have a heavier mass, wouldn't that more force, meaning more energy behind the swing, allowing it to go longer? That just seems to make sense to me, but i can't remember the physics of a pendulum off hand right now, which probably isn't good considering regionals is on saturday

### Re: It's About Time C

Posted: March 24th, 2010, 7:23 pm
i've never made a pendulum, but if you have a heavier mass, wouldn't that more force, meaning more energy behind the swing, allowing it to go longer? That just seems to make sense to me, but i can't remember the physics of a pendulum off hand right now, which probably isn't good considering regionals is on saturday
adding more weight will not help the time very much
it happens because of other forces such as friction and drag and especially the rigidness of the stand, if it sways with the swing your pendulum will not last long

### Re: It's About Time C

Posted: March 24th, 2010, 8:22 pm
For people that have been using rigid rod pendulums, what were your masses of the the pendulum and rod? I was trying out a rigid rod and it doesn't seem to last more that a 100 seconds.

My rod is 20 g while the mass I'm using is 250 g. Is weight of the rod the issue or the contact b/w the rod and axle? I'm using a single ball bearing (3/8 in inner diameter, 5/8 in outer diameter) to put them together fyi.
The contact between the rod and axle is more likely to be the issue. The weight of the rod should not be all that significant, though it could be an issue considering how similar the two are in your pendulum.
As I recall, Primate was having similar problems with his rigid pendulum, I think the issue turned out to be the bearing he was using, but you could ask him.
We use an extremely heavy weight at the bottom of our pendulum, several kilograms. Adding weight to the bottom would probably help, but the best way is just to try and see.

Also, the cycloid idea has been on these forums pretty much as long as Time has been around, and nobody has ever reported making one. I think it's too much work for too little return.

### Re: It's About Time C

Posted: March 24th, 2010, 9:57 pm
Just click on "Search" in the header menu of any page on these forums and enter "cycloid" in the "Search for Keywords" box. Scroll to the bottom of the page and click the "Search" button. Here's just one of the results returned.

### Re: It's About Time C

Posted: March 25th, 2010, 6:12 am
For people that have been using rigid rod pendulums, what were your masses of the the pendulum and rod? I was trying out a rigid rod and it doesn't seem to last more that a 100 seconds.

My rod is 20 g while the mass I'm using is 250 g. Is weight of the rod the issue or the contact b/w the rod and axle? I'm using a single ball bearing (3/8 in inner diameter, 5/8 in outer diameter) to put them together fyi.

Any help would be appreciated.
Use a bigger mass and look for friction. Ours swings for 25 minutes or more.

### Re: It's About Time C

Posted: March 27th, 2010, 7:13 am
For people that have been using rigid rod pendulums, what were your masses of the the pendulum and rod? I was trying out a rigid rod and it doesn't seem to last more that a 100 seconds.

My rod is 20 g while the mass I'm using is 250 g. Is weight of the rod the issue or the contact b/w the rod and axle? I'm using a single ball bearing (3/8 in inner diameter, 5/8 in outer diameter) to put them together fyi.

Any help would be appreciated.
Use a bigger mass and look for friction. Ours swings for 25 minutes or more.
WOW, what is the size of your mass?