Forum Discussion
Engineering Dynamics Problem
Hey all, Looking for some help for a dynamics/mechanical engineering problem. I am trying to find the minimum stopping distance of a truck given two coefficients of static friction (mu) when a 50 kg...
mtarler Thank you tons for introducing me to NAMES. I understand your concerns in the first portion of the comment and I thought the same thing at first. The sum of forces in the y-direction doesn't take into account the incline because of small angle approximation (i.e. it's really close to 1 so it would add unneeded complexity). For the coefficient of friction, we are assuming the truck is on an ice road and it's wheels are just about to slip, not already slipping because of modern technology like ABS. Hope that makes sense and makes you more confident in my equation.
I attached a few pictures of what my spreadsheet looks like and the equations/formulas I used. It seems like I went wrong somewhere because velocity drops to nearly zero immediately then rises as the cells move down. It should gradually decrease until velocity is zero, which would indicate the displacement (s) it traveled.
I might suggest you create a name TotWeight since you use that a lot. and i think you want to be using time change so cell B3 should be something like =D2*(A3-A2) but then again you can define dt as a name since it is a constant (you could make it =$A$3-$A$2 so if you change the step size it will automatically change with it. Another nice option is to define "Time Step" on the sheet (e.g. F1="Time Step =" and then in G1 you type what it will be like 0.02). And another quick trick/tip, with G1 highlighted you can click on the cell address in the top let to the left of the formula bar where is says 'G1' and then type "dt" and that will automatically create a "Name" called "dt" and set it to cell G1. Then in A2 you can type =SEQUENCE(1000,,,dt) to automatically create a column of 1000 numbers stepping by 'dt'. If you don't want to start at 0 then use =SEQUENCE(1000,,dt,dt)
I'm not clear why acceleration is changing. What is velocity dependent? Basically I don't get where that 0.9*V^2 comes in (looks like 1/2 m v^2 but that would be work not acceleration). I'm guessing that is another part of the problem not noted here.
Also in your notes you combine mu1 F1 + mu2 F2 to be mu*m*g which seems fine if mu1=mu2 but in your name definitions you indicate mu1=0.1 and mu2=0.2 so are the names wrong or the formula?
I'm not clear why acceleration is changing. What is velocity dependent? Basically I don't get where that 0.9*V^2 comes in (looks like 1/2 m v^2 but that would be work not acceleration). I'm guessing that is another part of the problem not noted here.
Also in your notes you combine mu1 F1 + mu2 F2 to be mu*m*g which seems fine if mu1=mu2 but in your name definitions you indicate mu1=0.1 and mu2=0.2 so are the names wrong or the formula?
