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Phy 201
Your 'cq_1_13.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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Seed Question 13-1
The purpose and the process of answering 'seed' questions:
In cloud seeding small crystalline particles (the 'seeds') are scattered throughout a cloud, so that water vapor in the cloud will build up on the 'seed' and eventually fall in the form of rain.
These questions are posed without any previous explanation. You are expected to use what you already know, along with common sense, to answer the questions. It is standard practice in many courses to an instructor to give explanations and examples before asking students to answer questions, and you will see plenty of examples and explanations in this course. However the goal here is to first experience and think about a situation. Whether you think correctly or incorrectly, your thinking gets you started on an idea and forms a 'seed' on which understanding can accumulate.
You are expected to answer it to the best of your ability, based on what you know at the beginning of this assignment.
You are not expected to research this question until after you have submitted your best response.
You are not penalized based on whether your answer is 'right' or 'wrong', but you are expected to think as clearly and deeply as you can about the question.
You are not, however, expected to spend hours thinking about the question or agonize unduly about your answers. A rule of thumb is to give it up to 20 minutes, half for thinking and half for typing in your answers (maybe a little more for the typing if you don't have good keyboard skills).
Your answers should consist of your best attempt at a solution, and/or one or more questions about the situation.
If you think you know the answer or can make a reasonable attempt to answer, then give your answer along with a concise outline of your reasoning.
If you aren't sure what the question is asking, make your best attempt to interpret and answer it, and consider including one or more questions.
If you are very sure you don't know what the question is asking, then break it down phrase-by-phrase or even word-by-word and explain what you think each key phrase or word might mean.
A question consists of a complete but concise statement of what you do and do not understand about the situation.
There are two ways you can spend an excessive amount of time explaining your solutions and/or asking questions. One is to type a lot more than what is necessary, and another is to spend a lot of time worrying about what is and is not necessary. Balance the two in the way that works best for you.
Remember that the 'concise' part is more for your benefit than mine. I can read a lot more quickly than you can type, and don't mind reading through a lot of words to understand your meaning.
You are invited but not required to include comments and/or discussion.
You are welcome to use reasonable abbreviations in your work.
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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.
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A ball rolls off the end of an incline with a vertical velocity of 20 cm/s downward, and a horizontal velocity of 80 cm/s. The ball falls freely to the floor 120 cm below.
For the interval between the end of the ramp and the floor, what are the ball's initial velocity, displacement and acceleration in the vertical direction?
V0 = 20cm/s, ds =120cm, a = 980cm/s^2
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What therefore are its final velocity, displacement, change in velocity and average velocity in the vertical direction?
Using the fourth equation
Vf = 485cm/s , ds = 120cm, dv = 465cm/s , Vave = 252.5cm/s
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What are the ball's acceleration and initial velocity in the horizontal direction, and what is the change in clock time, during this interval?
A = 0cm/s^2, v0 = 80cm/s, dt = .48s
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What therefore are its displacement, final velocity, average velocity and change in velocity in the horizontal direction during this interval?
Ds = 166.67cm, vf = 80cm/s, vAve = 80cm/s, dv = 0
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Moving at 80 cm/s for a little less than half a second, the ball won't move 167 cm.
You'll be able to figure out what you did wrong (I suspect you divided vAve by `dt, which doesn't make any sense and doesn't result in units of distance) and what you need to do to avoid such errors (e.g., use units, sketch, visualize, go back to definitions, etc.).
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After the instant of impact with the floor, can we expect that the ball will be uniformly accelerated?
I guess it could be depending on the surface it hits
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Why does this analysis stop at the instant of impact with the floor?
Thats a good question. Maybe because there are more variables involved after it hits the ground?
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There are, but the key is that the analysis assumes uniform acceleration, which ceases at the instant of contact with the floor.
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about 25 minutes. I was confused to begin with
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3/26/13 751pm
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Good, but you do have one error you'll want to reconcile. No need for a revision unless you have questions.
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