Assignment 4-2

course phy 201

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004. `Query 4

Physics I

02-15-2009

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assignment #004

004. `Query 4

Physics I

02-15-2009

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19:17:59

Intro Prob 6 given init vel, accel, `dt find final vel, dist

If initial velocity is v0, acceleration is a and time interval is `dt, then in symbols what are the final velocity vf and the displacement `ds?

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RESPONSE -->

vf = A('dt) + v0

'ds = .5(a)('dt)^2 + v0('dt)

confidence assessment: 2

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19:20:49

**You would use accel. and `dt to find `dv:

a * `dt = `dv. Adding `dv to initial vel. vo you get final vel.

Then average initial vel. and final vel. to get ave. vel.:

(v0 + vf) / 2 = ave. vel.

You would then multiply ave. vel. and `dt together to get the distance.

For example if a = 3 m/s^2, `dt = 5 s and v0 = 3 m/s:

3 m/s^2 * 5 s = 15 m/s = `dv

15 m/s + 3 m/s = 18 m/s = fin. vel.

(18 m/s + 3 m/s) / 2 = 10.5 m/s = vAve

10.5 m/s * 5 s = 52.5 m = dist.

In more abbreviated form:

a * `dt = `dv

v0 + `dv = vf

(vf + v0) /2 = vAve

vAve * `dt = `ds so

`ds = (vf + v0) / 2 * `dt.

**

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RESPONSE -->

ok i get it

self critique assessment: 2

your solution was fine

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19:26:33

What is the displacement `ds associated with uniform acceleration from velocity v0 to velocity vf in clock time `dt?

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RESPONSE -->

'ds = .5 * (vf^2 - v0^2) / A

confidence assessment: 2

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19:27:39

** Since accel is uniform vAve = (v0 + vf) / 2.

Thus displacement is

`ds = vAve * `dt = (v0 + vf) / 2 * `dt,

which is the first equation of uniformly accelerated motion. **

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RESPONSE -->

ok

self critique assessment: 3

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19:28:31

Describe the flow diagram we obtain for the situation in which we know v0, vf and `dt.

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RESPONSE -->

it is the acceleration flow diagram of v vs. t

confidence assessment: 3

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19:28:42

** The first level in the diagram would contain `dt, v0 and vf.

Then v0 and vf would connect to `dv in the second level.

The second level would also contain vAve, connected from vf in the first level to v0 in the first level.

The third level would contain an a, connected to `dv in the second level and `dt in the first level.

The third level would also contain `ds, connected to vAve in the fourth level and `dt in the first level. **

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RESPONSE -->

ok

self critique assessment: 3

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19:29:41

Query Add any surprises or insights you experienced as a result of this assignment.

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RESPONSE -->

i actually realized that i'm going through too many steps and am trying too hard to get to the solutions of different equations given certain information. if i could simplify things i would reach a correct answer quicker.

confidence assessment: 3

That will occur naturally as you progress through the course. You're diong very well.

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19:29:48

** Student Response: I think I really confused what information stood for what in the Force and Pendulum Experiment. However, I enjoy doing the flow diagrams. They make you think in a different way than you are used to. INSTRUCTOR NOTE: These diagrams are valuable for most people. Not all--it depends on learning style--but most. **

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RESPONSE -->

ok

self critique assessment: 3

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&#This looks good. See my notes. Let me know if you have any questions. &#