# NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/

## JDK1.0.2 simulations (1996-2001) => Dynamics => Topic started by: swimz on May 02, 2006, 01:14:43 pm

 Title: law for levers Post by: swimz on May 02, 2006, 01:14:43 pm Hi found this question in a book and can seem to find any answers to it. So hpe u can help!Archimedes is suppose to have said "give me a lever long enough and a fulcrum on which to place it, and I shall move the world." Explain the physics behind Archimedes thinking. thanks :) Title: topic363 Post by: Fu-Kwun Hwang on May 02, 2006, 02:17:56 pm Hints: Torque = r X F if r getting larger , then ... Title: topic363 Post by: swimz on May 02, 2006, 04:20:29 pm is "r" suppose to mean the distance?torque is directy proportional to the distance and force. so if r is getting larger, this means that the force will also increase. How does this relate to the question? :?:  lolthanks Title: topic363 Post by: Fu-Kwun Hwang on May 02, 2006, 05:22:42 pm The mass of the earth is very large. You need a strong force to let the movement noticeable.Torque = r1 X F1 = r2 XF2If r1 is large enough, You can have very large F2 if r2 is small.  Or r1/r2>>1 Title: topic363 Post by: rhipple on May 02, 2006, 11:30:47 pm I pondered this question a while ago. It boils down to replacing a large force acting through a short distance with a small force acting through a large distance. Title: Re: law for levers Post by: christit76 on February 22, 2007, 03:15:42 am I have a question. I had an experiment using a meter stick, pencil (round without flat sides), quarter(new state one) and penny (1981 or later one).  I had to balance the meter stick on the pencil to find the center of gravity. It was 45.5. I then placed the quarter on 32 cm. To balance the quarter, I had to place the penny on 81 cm.  So c.g.= 45.5cm   x= 81cmEquation reads as follows:L1=c.g.-32=___-32,  L1=___cmscalculate L2= m1/m2 (L1)=____ (    );  L2=____cmsexperimental L2=  x-c.g. when stick is balancedL2=_____-______;  L2= _____ cms                             (experimental)Percentage error= larger-smaller/calculated value  x 100Percentage error= (       )-(        )/(        )   x 100Percentage error=_________%I put 13.5 on the first blank and -18.5 on the second. On the m1/m2 blank, I put 32/81 (-18.5) ; L2=      -7.31   On the experimental L2= 81-45.5=35.5.  Please let me know if I am doing this correctly. I don't know even where to begin with the percentage error.  Can you please help???????????? Title: Re: law for levers Post by: Fu-Kwun Hwang on February 22, 2007, 04:19:50 pm You should have put 45.5 on the first black , which will give you L1=13.5 on the second. And you can work  out the rest.For Percentage error: find the (larger and smaller value) from the (calculated L2 and experimental L2).