okay we're going to continue to look at acceleration and specifically we're going to look at what it means what physical meaning how should i think about an acceleration that's positive how should i think about an acceleration that's negative and how to connect that information the positive or negative acceleration with the actual problem i'm looking at to see whether the object itself is speeding up as it says here which is acceleration or slowing down which is deceleration either can be true for a given acceleration as we're going to see the key to your analysis when trying to understand whether the acceleration in a given problem means speeding up acceleration or slowing down deceleration is to look at the initial velocity direction for the velocity vector and then look at the sign the positive or negative of the acceleration that will tell you right away whether your problem is talking about accelerating or decelerating so again acceleration is a little tricky because we have kind of two two aspects to our verbiage one is the general use of the word acceleration right which then is broken down into speeding up or slowing down so let's see what's going on so if we start with an initial velocity backwards of 5 meters per second so that's the negative 5 meters per second that we have here our initial velocity if our acceleration itself is negative notice negative and negative negative acceleration negative initial velocity that means speeding up the acceleration was pulling backwards on the velocity vector which was already backwards so it was speeding up so in this case negative 10 meters per second squared means speeding up accelerating so the acceleration is pulling the velocity to the left at 10 meters per second every second so for this example negative 10 means speeding up well negative 10 can also mean slowing down what if instead of initially going backwards we were initially going forward well the acceleration is still pulling to the left at 10 meters per second every second so we are indeed slowing down so our negative 10 meter per second squared acceleration in this example means decelerating slowing down so this page of notes is really important it was really short to go through and annotate just three minutes into our our notes we're really done with with the bulk of it but it shows you that you can never look at a problem and be given the acceleration negative 10 and right away say oh that means the object is speeding up or oh that means the object is slowing down you have to look at the initial velocity value if you understand this page of notes then you know to answer the question is very easy if the acceleration if the acceleration and the initial velocity are in the same direction either both backwards or both forwards that means you're speeding up if the acceleration and the initial velocity are in opposite directions opposite at all so the acceleration can be backward the velocity forward or the velocity backwards the acceleration forward if they're opposite then that means slowing down so again really important page of notes acceleration can be tricky you have to really latch on to what is being covered here with acceleration what acceleration is actually doing and this notion that acceleration means both speeding up accelerating or slowing down decelerating so we'll have some examples to do and of course we'll talk about it when we're together in class