1. The problem statement, all variables and given/known data A particle is traveling in a straight line at a constant speed of 24.5 m/s. Suddenly, a constant force of 14.3 N acts on it, bringing it to a stop in a distance of 52.9 m. a. Determine the time it takes for the particle to come to a stop. b. What is its mass? 2. Relevant equations 1. vx2 = v0x2 +2a[tex]\Delta[/tex]x 2. [tex]\Delta[/tex]x = v0t + 0.5at2 3. F=ma 3. The attempt at a solution I know how to solve part a. I use equation 1 to find a which is 5.673 m/s^2 I use that value of a in equation 2 to find t which is 4.318 s This is all correct. I am having trouble with part b - to find mass. The only equation I have to find mass is f=ma F is 14.3N given, a as calculated is 4.318 which gives m as 3.311 kgs which is incorrect. The correct answer is 2.52 kg So I thought that for F=ma, F must be the resultant force of some sort. So I subtracted 24.5-14.3 (which I am sure is not a correct step to do) gives me 10.2 And that divided by a (4.318) gives me m as 2.362 which is close but not correct. Any other thoughts? Thanks so much EDIT: Aarggghh.. stupid me I am diving by t (4.318) instead of the a I found (5.673). Can't believe I spent so much time on this stupid stupid mistake.