Assignment 2

This appears to be the 'open' query, except that many key words and prompts are missing. Without these key words and prompts, I can't easily distinguish your answers from the rest of the document.

You need to submit a copy of the document with your responses inserted, and except for your responses, which need to be inserted at the appropriate points, nothing else in the document should be changed.

Please insert your answers into a complete copy of the 'open' qa and submit that document. You can just copy-and-paste from the answers you gave here, which shouldn't take more than 10 minutes. I've included a copy of the 'open' qa below, in case that's more convenient for you.

If your solution to stated problem does not match the given

.

Your solution, attempt at solution.

002.  `ph1 uery 2

NOTE PRELIMINARY TO QUERY:

**  Questions about velocity, average velocity,

It is essential to keep the definitions and the meanings of

That inevitably takes people a little time.  But in the

Question:  How is acceleration an example of a rate

Your solution: 

Confidence Assessment:

Given Solution: 

** Velocity is the rate of change of position. 

To find the acceleration from a v vs. t graph you take the

The average rate of change of velocity with respect to

Self-critique (if necessary):

Self-critique Rating:

Question:  If you know average acceleration and time

Your solution: 

Confidence Assessment:

Given Solution: 

** Accel = change in vel / change in clock time, so if you

In this case you don't know anything about how fast the

COMMON ERROR (and response):  Average acceleration is the

INSTRUCTOR RESPONSE: Acceleration is rate of change of

COUNTEREXAMPLE TO COMMON ERROR:  Moving at a constant 60

COMMON ERROR and response:  You can find displacement

INSTRUCTOR RESPONSE:  From average velocity and time

However from average acceleration and time interval you can

Self-critique (if necessary):

Self-critique Rating:

Question:  Can you find velocity from average

Your solution: 

Confidence Assessment:

Given Solution: 

** Ave accel = change in vel / change in clock time.  If

Change in clock time is the time interval, so if we know

We cannot find velocity, only change in velocity.  We would

For example if we know that the velocity of a car is

If this car had originally been going 20 mi/hr, it would

Similarly if an object is accelerating at 30 m/s^2 (i.e.,

ANOTHER SOLUTION:

The answer is 'No'. 

You can divide `ds (change in position) by `dt (change in

Or you can divide `dv (change in vel) by `dt to get aAve. 

So from aAve and `dt you can get `dv, the change in v. 

But you can't get v itself.

EXAMPLE:  You can find the change in a quantity from a rate

COMMON ERROR: Yes. Final velocity is average velocity

INSTRUCTOR RESPONSE: We aren't given ave velocity and time

Note also that final velocity is average velocity

ANOTHER EXAMPLE:

You can't find velocity from ave accel and time

You can find the change in velocity.  The actual velocity

Self-critique (if necessary):

Self-critique Rating:

Question:  `qCan you find change in velocity from

Your solution: 

Confidence Assessment:

Given Solution: 

Average acceleration is ave rate of

Given average acceleration and time

The obvious use of these quantities is

• aAve * `dt = `dv / `dt * `dt = `dv

So with the given information aAve and `dt,

From this information we can find

`a**Good student response: 

Yes, the answer that I provided previously is wrong, I

Change in velocity is average accel * `dt.

CALCULUS-RELATED ANSWER WITH INSTRUCTOR NOTE(relevant

Yes, you take the integral with respect to time

INSTRUCTOR NOTE: 

That's essentially what you're doing if you multiply

In calculus terms the reason you can't get actual velocity

IMPORTANT INSTRUCTOR NOTE: 

I do not use v or the

unmodified term 'velocity' for anything at this stage of the

course, and despite the fact that your textbook does, you should at

this stage consider avoiding it as well.

At this point in the course the word 'velocity' should always

be modified by an adjective.

Motion on any interval

involves the following quantities, among others:

• initial velocity v0, the velocity at the

  beginning of the interval

• final velocity vf, the velocity at the end

  of the interval

• average velocity vAve, defined as average

  rate of change of position with respect to clock time, `ds / `dt

• change in velocity `dv, which is the

  difference between initial and final velocities

• (midpoint velocity

  vMid), which is the same as vAve provided
  the v vs. t graph is linear (i.e., provided acceleration is constant);
  since most motion problems will involve uniform acceleration this
  quantity will be seen than the others

If you aren't specific about which velocity

you mean, you will tend to confuse one or more of these

quantities.

The symbol v, and the

unmodified term 'velocity', have more complex and ambiguous

meanings than the specific terms outlined above:

• The symbol v

  stands for 'instantaneous velocity', a concept that is
  challenging to understand well
  without a calculus background (which isn't expected or
  required for your the General College Physics or
  Principles of Physics courses). Your
  text (along with most others) uses v to stand for the
  instantaneous velocity at clock time t,
  but sometimes it uses the symbol v for the average
  velocity.   

• To denote an

  instantanous velocity I consider it more appropriate
  to use the functional notation v(t).,
  which clearly denotes the velocity at a specific
  instant.

The ambiguous use of the word

'velocity' and the symbol 'v' are the source of almost

universal confusion among students in non-calculus-based

physics courses.  (Students in calculus-based courses are

expected to have the background to understand these

distinctions, though most such students can also profit

from the specific terminology outlined here.

Self-critique (if necessary):

Self-critique Rating:

Question:  `qCan you find average velocity from

Your solution: 

Confidence Assessment:

Given Solution: 

`a** CORRECT STATEMENT BUT NOT AN ANSWER TO THIS QUESTION:

The average acceleration would be multiplied by the time

INSTRUCTOR RESPONSE: 

Your statement is correct, but as you say you can find

You cannot find ave vel. from just accel and time

CALCULUS-RELATED ERRONEOUS ANSWER AND INSTRUCTOR

Yes, you take the integral and the limits of integration at

CLARIFICATION BY INSTRUCTOR:

A definite integral of acceleration with respect to t gives

To find the average velocity you would have to integrate

Self-critique (if necessary):

Self-critique Rating:

Question:  `qYou can find only change in velocity

Your solution: 

Confidence Assessment:

Given Solution: 

**  Average velocity is change in position/change in clock

CALCULUS-RELATED ANSWER you dont know the inital velocity

INSTRUCTOR COMMENT: 

 . . . i.e., you can't evaluate the integration constant.

Self-critique (if necessary):

Self-critique Rating:

Question:  `qGeneral College Physics only:  Problem

Your solution: 

Confidence Assessment:

Given Solution: 

** Radius 2.8 * 10^4 cm means that the radius is between

This means that the area is between pi * (2.75 * 10^4 cm)^2

Note that the .1 * 10^4 cm uncertainty in radius is about

Self-critique (if necessary):

Self-critique Rating:

Question:  `q Query   Add comments on any surprises

Your solution: 

Confidence Assessment:

Given Solution: 

** COMMON STUDENT COMMENT AND INSTRUCTOR RESPONSE:  I am

RESPONSE: 

I note that you are expressing most of your answers in the

The concepts of velocity, acceleration, etc. are very

If you look at the Linked Outline (on the main Physics 1

Also the Introductory Problem Sets give you formulas in the

Self-critique (if necessary):

Self-critique Rating:

Question:  `qPrinciples of Physics Students and

Your solution: 

Confidence Assessment:

Given Solution: 

Presumably you know your height in feet and inches, and

To get your height in meters, you would first convert your

Thus if you multiply your height in inches by 2.54 cm / (1

in * cm / in = (in / in) * cm = 1 * cm = cm, so our

Self-critique (if necessary):

Self-critique Rating: