course phy 201
Your work has been received. Please scroll to the end of the document to see any inserted notes (in boldface) and a note at the end. The note at the end of the file will confirm that the file has been reviewed; be sure to read that note. If there is no note at the end, notify the instructor through the Submit Work form, and include the date of the posting to your access page.
Question 4 Version 1An automobile traveling a straight line is at point A at clock time t = 4 sec, where it is traveling at 10 m/s, to point B at clock time t = 11 sec, where it is traveling at 20.5 m/s. Point A is 75 meters from the starting point and point B is 115 meters from the starting point. What are the average velocity and the average acceleration of the automobile during the specified time? What evidence is there that the acceleration is or is not uniform?
The average velocity will be in the middle of the two velocities. Which is (20.5m/s + 10m/s) /2 = 15.25m/s
Average velocity is change in position / change in clock time.
If acceleration is uniform, then the v vs. t graph is a straight line and the average velocity is the average of initial and final velocities--as you put it, the average velocity is in the middle of the two velocities.
It follows that if the velocity in the middle is not the average velocity, then acceleration couldn't have been uniform.
What is the average velocity here, and is it equal to your 'velocity in the middle'?
What therefore can you conclude, if anything, about the uniformity of the acceleration?
The average acceleration can be found by finding the time interval which is 7seconds and you find this by subtracting 4 seconds from 11 second. You then find the change in velocity which is 20.5m/s – 10m/s = 10.5m/s…. you then take the change in velocity and divide it by the time interval.
10.5m/s / 7s = 1.5m/s^2
The acceleration is not uniform because the change in velocity is not equal to average velocity. If they were equal then you would have a uniform acceleration but since they are no then you don’t.
Change in velocity can be equal to average velocity. For example if you accelerate uniformly from 5 m/s to 15 m/s over a period of time, the average velocity and change in velocity are both 10 m/s.
Good try, but there are a couple of errors in your reasoning.
Please send me a revision, and/or questions, guided by my notes.