assignment 4 query

course Phy 121

~PM|~assignment #004

004. `Query 4

Physics I

02-10-2009

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17:26:40

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 -->

v0+'dv=vf and 'ds=(v0+vt)/2* 'dt

confidence assessment: 2

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17:28:56

**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 -->

wrote in average velocity instead of distance

self critique assessment: 3

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17:30:00

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=(v0+vf)/2* 'dt='dt*vAve

confidence assessment: 2

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17:30:08

** 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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17:34:37

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

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RESPONSE -->

top of flow diagram would contain all three. v0 and vf are part of the vAve equation so they would both connect to it. v0 and vf would also connect to a 'dv. then the 'dv would have an 'a' and a dt' stemming off of it.

confidence assessment: 2

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17:34:43

** 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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17:36:12

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

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RESPONSE -->

thought the experiment with the dice was interesting

confidence assessment: 3

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17:36:20

** 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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&#Very good responses. Let me know if you have questions. &#