I'm having a little trouble with the wording in this problem. (And this isn't the first time). My instructions are: "Draw a pictorial representation of each situation described below. That is, (i) sketch the situation, showing appropriate points in the motion, (ii) establish a coordinate system on your sketch, and (iii) define appropriate symbols for the known and unknown quantities. Do not solve. a) A car traveling at 30m/s screeches to a halt, leaving a 55m long skid mark. What was the car's acceleration while braking? So am I solving the cars acceleration or not? So far I've gotten my known as the velocity 30m/s, my unknowns would be displacement and acceleration, and a very rough picture of a car and an arrow showing forward motion with 30m/s under it and then a line indicating the 55m skid mark. I have no idea what it's really asking me to do though. Do I solve it? (It says not to be then asks a very specific question.) I'm so confused.