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

## Easy Java Simulations (2001- ) => Collaborative Community of EJS => Topic started by: lookang on January 10, 2011, 08:50:50 am

 Title: Ejs Open source Primary Distance & Speed time java applet Post by: lookang on January 10, 2011, 08:50:50 am Ejs Open source Displacement & Velocity time java appletEjs Open source Primary Distance & Speed time java appletvariant simulation for Primary Maths.http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=750.0finer customized for Primary school maths Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 10, 2011, 08:53:48 am changes1 remove acceleration according to primary school teacher.2 unit in km/h instead of m/s according to primary school teacher.3 further bug reduction4 axis for x is further refine to follow xming = Math.min(x1,xmin);xming = Math.min(x2,xming); //  for maximum view instead of autoscale which is suppose to be difficult for young minds5 fix PY1[1] and PY2[1] at the top left corner to follow the distance of the rectangle6 fix the time to reflect the distance as accurate as possible for given t = 0.00s7 use // screen view if(x1if(x1>xmax) xmax*=1.2; if(x2if(x2>xmax) xmax*=1.2;  instead of 48 change context to cars (from microsoft clipart) as to travel in km/h9 added town A and B selectable to a maximum of 10 to 1000 km to suit most problem.10 time is input field to suit questions that require going backwards in time Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 12, 2011, 03:52:25 pm Question 1RED drove from Town A to Town B at a uniform speed. At 2/3 of the journey, RED passed his neighbor, YELLOW, who started from Town A earlier. YELLOW was driving his car at an average speed of 72km/h. 3 hours later, RED arrived at Town B. YELLOW was still 40km away from Town B. What was the distance between Town A and Town B?Solution72 x 3 = 216216 + 40 = 256256 x 3 = 768 km Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 12, 2011, 03:54:54 pm Question 2A RED car was on its way from Town A to Town B. After covering 2/5 of its journey, it passed a YELLOW car which was moving at an average speed of 70 km/h. 5 h later, the RED car reached its destination, but the YELLOW car was still 28 km from town B. If the YELLOW car had also started from town A, how long would it take to travel from Town A to Town B?Solution70 x 5 = 350350 + 28 = 378378 ÷ 3 = 126126 x 5 = 630630 ÷ 70 = 9 h Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 12, 2011, 03:57:00 pm Question 3RED and YELLOW have a race. RED cycles at a speed of 12 km/h. YELLOW cycles at speed of 16km/h. If YELLOW lets RED start 40 min before him, how long will YELLOW take to catch up with RED?Solution16 – 12 = 412 x(40/60)   = 88 ÷ 4 = 2 h  Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 12, 2011, 03:58:18 pm Question 4The distance between Town A and Town B was 540 km. RED car took 6 hours to travel from Town A to Town B. A YELLOW car took 12 hours to travel from Town B to Town A. Both the RED car and the YELLOW car started their journey at noon. At what time would they pass each other along the same road?12 X 6 = 72      6 + 12 = 18      72/18  = 4       They will pass each other at 4 p.m. Title: Re: Ejs Open source Displacement & Velocity time java applet Post by: lookang on January 12, 2011, 04:01:02 pm Question 5A RED car took 2 h to travel from town X to town Y. His average speed for the whole journey was 40 km/h. For the first   of the journey, he traveled at an average speed of 50 km/h. Find his average speed for the second part of the journeySolution   2  X 40 = 100 km    100 X (1/4)   = 25 km   100 – 25 = 75 km                  time taken for (1/4)  of journey    = 25/50                          =  1/2 h   time taken for 2nd part of journey    = 2.5  – 0.5                      = 2h   Average speed = 75km /  2                      = 37.5km/h            or   2.5  X 40 = 100 km   100 x (3/4) = 7575 ÷ 2 = 37.5 km/h