#$&*
phy 201
Your 'cq_1_06.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
Copy the problem below into a text editor or word processor.
• This form accepts only text so a text editor such as Notepad is fine.
• You might prefer for your own reasons to use a word processor (for example the formatting features might help you organize your answer and explanations), but note that formatting will be lost when you submit your work through the form.
• If you use a word processor avoid using special characters or symbols, which would require more of your time to create and will not be represented correctly by the form.
• As you will see within the first few assignments, there is an easily-learned keyboard-based shorthand that doesn't look quite as pretty as word-processor symbols, but which gets the job done much more efficiently.
You should enter your answers using the text editor or word processor. You will then copy-and-paste it into the box below, and submit.
For each situation state which of the five quantities v0, vf, `ds, `dt and a are given, and give the value of each.
• A ball accelerates uniformly from 10 cm/s to 20 cm/s while traveling 45 cm.
answer/question/discussion: ->->->->->->->->->->->-> :
v0 = 10 cm/s
vf = 20 cm/s
`ds = 45 cm
`dt = 3 s
a = 3.33 cm/s/s
Work:
vAve = `ds / `dt
((20 cm/s + 10 cm/s) / 2) = 45 cm / `dt
15 cm/s = 45 cm / `dt
`dt * 15 cm/s = 45 cm
`dt = 3 s
aAve = `dv / `dt
aAve = 10 cm/s / 3 s
aAve = 3.33 cm/s/s
#$&*
• A ball accelerates uniformly at 10 cm/s^2 for 3 seconds, and at the end of this interval is moving at 50 cm/s.
answer/question/discussion: ->->->->->->->->->->->-> :
v0 = 20 cm/s
vf = 50 cm/s
`ds = 105 cm
`dt = 3 s
a = 10 cm/s/s
Work:
aAve = `dv / `dt
10 cm/s/s = (50 cm/s - v0) / 3 s
30 cm/s = 50 cm/s - v0
20 cm/s = v0
vAve = `ds / `dt
((50 cm/s + 20 cm/s) / 2) = `ds / 3 s
35 cm/s = `ds / 3s
105 cm = `ds
#$&*
• A ball travels 30 cm along an incline, starting from rest, while accelerating at 20 cm/s^2.
answer/question/discussion: ->->->->->->->->->->->-> :
v0 = 0 cm/s
vf = 10.95 cm/s
`ds = 30 cm
`dt = .55 s
a = 20 cm/s/s
Set up equations:
aAve = `dv / `dt
20 cm/s/s = (vf - 0) / `dt
20 cm/s/s * `dt = (vf - 0)
`dt = (vf - 0) / 20 cm/s/s
vAve = `ds / `dt
((vf + 0)/2) = 30 cm / `dt
Work:
# ((vf + 0)/2) = 30 cm / ((vf - 0)/20cm/s/s)
vf / 2 = 30 * (20 cm/s/s / vf)
vf / 2 = 60 / vf
vf^2 / 2 = 60
vf^2 = 120
sqrt(vf^2) = sqrt ( 120)
vf = 10.95 cm/s
# `dt = (vf - 0) / 20 cm/s/s
`dt = (10.95 cm/s / 20 cm/s/s)
`dt = .55 s
#$&*
Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
answer/question/discussion: ->->->->->->->->->->->-> :
It was possible to determine vAve directly from the information given in the first problem because I was given v0 and vf.
In the second and third problems, I had to indirectly determine vAve, finding other values before I had the information to solve for vAve.
#$&*
• Is it possible to directly determine `dv?
answer/question/discussion: ->->->->->->->->->->->-> :
Again, it was possible to determine `dv directly from the information given in the first problem because I was given v0 and vf.
In the second and third problems, I had to indirectly determine `dv, finding other values before I had the information to solve for `dv.
#$&*
** **
30 minutes
** **
&#Good responses. See my notes and let me know if you have questions. &#