Acceleration: Constant, Instataneous and the Various Formulae

The class started with Mr.Banow saying a enthusiastic good morning and Jordan talking about the physics behind a toy bow and arrow (unfortunately I was not here for the presentation and so am unable to repeat what was discussed. I'm also assuming Mr. Banow said hi!). Following his presentation he continued to shoot the arrow at Unger.

The previous day the class had begun to work on questions to do with acceleration. The questions were found on page 62, 67 and 69. On page 62, you had to find acceleration using the formula $a=(vf-vi)/(t2-t1)$. On page 67 you not only had to find acceleration but also instantaneous acceleration. That was accomplished by using the formula $a'inst=change in v/ change in t$. On page 69 a velocity vs time graph was given. The question asked that the graph given be converted into another two graphs: a distance vs time graph and a acceleration vs time graph. To create the distance vs time graph, the area of different sections needed to be found to make the points on the graph. To create an acceleration vs time graph the acceleration needs to be calculated [using the formula for acceleration]. The parts with slope indicate acceleration while those that are straight on the velocity vs time graph indicate that this is no acceleration and therefore are found at the x axis on the acceleration graph.



As seen on this graph, there is no acceleration for the first two seconds. On a velocity time graph this would be a straight line. From 2 to 4 seconds this indicates that the acceleration has changed. On the velocity time graph, this part would have a slope. The last section of 4 to 6 seconds indicates that there is no acceleration again. The velocity time graph would be a straight line again.

The class continued after the questions were completed and Mr.Banow turned on the handy dandy smart board. We then looked at constant acceleration formulas. No notes were taken but the class watched an applet to do with a car. The applet showed the different graphs that occured with different motions the car performed such as maintaing a constant velocity, speed and acceleration.



Example 1) A car going constant speed showed the following graphs-*note ignore the numbers from these graphs as they are taken from different source. The shape they create is what is to be observed!

Distance








Velocity








Acceleration





Example 2) When we changed the initial velocity of the car, had an acceleration of (-1) and changed the distance, the following graphs resulted:






Distance







Velocity







Acceleration





The class went back to looking at the formulas that were seen before the applet. The formulas given (found on the handout from yesterday) can only be used if the acceleration is constant! We began to go over the question on a handout dealing with acceleration that had a variety of formulas given. The best choice had to be chosen based on the information given and what you had to solve for. The Graphs on page 69 were announced due for tuesday at the end of class.



Jillian is next :)