Re: Mechanical Systems Question

*To*: mathgroup at smc.vnet.net*Subject*: [mg14854] Re: Mechanical Systems Question*From*: "vdmcc" <w.meeussen.vdmcc at vandemoortele.be>*Date*: Fri, 20 Nov 1998 02:17:01 -0500*Organization*: EUnet Belgium, Leuven, Belgium*References*: <72tqhj$iml@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

hi Rich, I'd say that the distance travelled is the integral over the instantaneous speed, or the average speed times elapsed time ; for constant decelleration, the average speed is half the initial speed, so the time nescessary is t = s/(v/2) and a= - v/ t = - v^2 /( 2 s ) or abouts. For your example that would be a= - 4^2 /( 2 * 25) = - 0.32 m/s^2 You learn to do stuff like that in your head after a while. wouter. Richard Cooper wrote in message <72tqhj$iml at smc.vnet.net>... >Hi All, > >I am using Mechanical Systems and need help modelling motion where the >velocity of a body is dependent on its distance from a set point. > >For example, I have a body moving in 1D which starts with a speed of 4 >m/s and is subject to a constant but unknown deceleration. The point at >which the body comes to rest must be 25 m from the starting point. > >What is the best way to model this system (and calculate the >decleration)? > >The following might be a good starting point. It needs one more >constraint. > >fixed = 1; >flyer = 2; >start = {0, 0}; >pointOfRest = {0, 25}; > >SetConstraints[ > RotationLock1[1, flyer, fixed, 0], > RelativeY1[2, Point[flyer, 0], 0], > DirectedDistance1[3, Point[flyer, 0], start, {1, 0}, 4T-(a T^2)/2], > Constraint[5, {}, {a, 1}] >] > >Cheers, > >Rich. >