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View Full Version : NEED Easy physics/science help. (LEVERAGE)

legendboy
01-19-2004, 01:20 PM
Can someone please explain the variables and formula to calculate the following. (x amount of force exerted on the drive rod, x length of lever arm, x amount of force exerted to rod being driven (black)) Thanks

http://www.telusplanet.net/public/kaake/Lever.jpg

cycosis
01-19-2004, 01:22 PM
Original Post Removed. (Please read the Forum Rules and Terms of Use (http://forums.beyond.ca/articles.php?action=data&item=1) before posting again, or risk getting banned).

kaput
01-19-2004, 07:36 PM
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ninjak84
01-19-2004, 07:55 PM
Since you have 3 unsolved variables to solve for, you need to know the mass and velocity of the initial force acting on the Drive Rod.
Once you know them, use the formula Force = (mass x change in velocity) / (change in time)
Use whatever change in time as suites the function of the Drive Rod. Depending on how the Drive Rod and Driven Rod work, you could probably substitue RPM for velocity.
Now, you can use the formula (mass before) x (velocity before) = (mass after) x (velocity after) to solve for the third rod's force exerted.

Since momentum = mass x velocity, and change in time x force exerted = mass x change in velocity, all of the values you get for force should be correct. Don't forget to use "0" as your initial velocity. Also, it would help to draw a vector diagram and use the laws of sine, cosine, and tangent as you go along.

Someone let me know if I messed up somewhere.... That hardly made sense to me as I was typing it out, but it should all prove itself!

kaput
01-19-2004, 08:04 PM
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ninjak84
01-19-2004, 08:13 PM
Originally posted by kaput
I don't understand anything you just did :confused:

The vector diagram has to include all directions of the force on the Drive and Driven rods, then you can calculate the length of the level arm (using sin, cos, tan).
The momentum and force equations are there to prove eachother, and they should give you the values of the force exerted on the Drive and Driven Rods. Remember, everything in the system that legendboy drew is a vector quantity.

There's probably a ton of ways to solve for this question, this is only one.

ninjak84
01-19-2004, 08:56 PM
Here's another way to solve for the force exerted on the Drive and Driven rods.

Power = (Force x Distance) / (time)

Rearrange the formula to solve for force, and input your variables.

JustinL
01-19-2004, 09:41 PM
Ninja-- I think you are overanalyzing the problem. This looks to me like a static situation.

Legend boy-- Kaput is right, we need a little better diagram. We need to know WHERE the forces are acting as well as the magnitude and direction and some information about the angles and distances of the triangles.

Can you also clarify what you are asking? I have a feeling that you are being asked for the moments and not the forces. If it's just the forces, then the force being applied to the drive rod= the force being applied to the drive rod ;)

Justin

kaput
01-19-2004, 10:42 PM
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