Phy 201
Your 'cq_1_02.2' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
The problem:
A graph is constructed representing velocity vs. clock time for the interval between clock times t = 5 seconds and t = 13 seconds. The graph consists of a straight line from the point (5 sec, 16 cm/s) to the point (13 sec, 40 cm/s).
• What is the clock time at the midpoint of this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Halfway between 5 s and 13s is 9s, increments of 4 seconds. The clock time at midpoint of this interval is 9 sec
#$&*
• What is the velocity at the midpoint of this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Halfway between 16cm/s and 40cm/s is 28cm/s, increments of 12 cm/sec. The velocity at midpoint of this interval is 28 cm/sec
#$&*
• How far do you think the object travels during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
If the velocity is 16cm/s = X / 5 sec, then you multiply 16 cm/s by 5 sec to get the number of cm at the moment (80cm) and 40 cm/s = X/ 13 sec you multiply 40 cm/s by 13 sec to get 520 cm. So the object goes from 80 cm to 520 cm. You subject 80 from 520 to get 440 cm. I think the object travels 440 cm during this interval
You've done some good thinking, but you've made some extraneous assumptions. As you'll see when you check the link at the end, it's actually simpler that this, and I believe you'll understand.
#$&*
• By how much does the clock time change during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The clock time changes by 8 seconds during this interval. You subtract 5 sec by 13 sec.
#$&*
• By how much does velocity change during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The velocity changes 24 cm/s during this interval. You subtract 16 cm/s by 40 cm/s.
#$&*
• What is the average rate of change of velocity with respect to clock time on this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
average rate= change in velocity/ change in clock time
(40 cm/sec – 16 cm/sec)/(13 sec-5sec) = 3.5 cm/sec
The average rate of change of velocity with respect to clock time on this interval is 3.5 cm/sec
Very good, but check your arithmetic (24 / 8 = 3, not 3.5), and check out the correct units of this result
#$&*
• What is the rise of the graph between these points?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The rise of the graph is 4 sec between these points
#$&*
• What is the run of the graph between these points?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The run of the graph is 12 cm/sec between these points
you have rise and run between initial and midpoint, but not between initial and final
#$&*
• What is the slope of the graph between these points?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The slope of the graph between these points is (9sec, 28cm/sec)
That's the correct midpoint, but it's not the slope.
#$&*
• What does the slope of the graph tell you about the motion of the object during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The slope of the graph is positive and tells you that the motion of the object during the interval is moving forward in a positive direction and is increasing speed.
#$&*
• What is the average rate of change of the object's velocity with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
average rate= change in velocity/ change in clock time
(40 cm/sec – 16 cm/sec)/(13 sec-5sec) = 3.5 cm/sec
The average rate of change of velocity with respect to clock time on this interval is 3.5 cm/sec
#$&*
** **
35 minutes
** **
You've got a good start here; see my notes, check the link and you should submit a revision so we can be sure you understand everything.
&#See any notes I might have inserted into your document. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#