course Phy 201 ò…må‡éƒñ¸ðüØ¢çöø`wÏ„ÞŒýÁáassignment #005
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22:36:42 Intro Prob 6 Intro Prob 6 How do you find final velocity and displacement given initial velocity, acceleration and time interval?
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RESPONSE --> Multiply aAve by `dt to get `dv. Add `dv to vo to find vf. Subtract vo from vf and divide the answer by 2 to get vAve. Multiply vAve by the `dt to find `ds. confidence assessment: 2
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22:37:41 ** To find final velocity from the given quantities initial velocity, acceleration and `dt: Multiply `dt by accel to get `dv. Then add change in velocity `dv to init vel , and you have the final velocity**
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RESPONSE --> ok self critique assessment: 3
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22:44:54 Describe the flow diagram we obtain for the situation in which we know v0, vf and `dt.
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RESPONSE --> vo, vf and `dt are on the 1st level. vf-vo = `dv, which goes on the 2nd level. We can also find vAve by subtracting vo from vf and dividing the answer by two, so vAve is on the 2nd level as well. vAve and `dt can be multiplied to find `ds, which would be on the 3rd level. On this level we also can find aAve by dividing `dv by `dt. confidence assessment: 2
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22:45:25 ** The flow diagram shows us the flow of information, what we get from what, usually by combining two quantites at a time. How we get each quantity may also be included. From vf and v0 we get `dv, shown by lines from vf and v0 at the top level to `dv. From vf and v0 we also get and vAve, shown by similar lines running from v0 and vf to vAve. Then from vAve and `dt we get `ds, with the accompanying lines indicating from vAve and `dt to `ds, while from `dv and `dt we get acceleration, indicated similarly. **
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RESPONSE --> ok self critique assessment: 3
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22:58:41 Principles of Physics and General College Physics Students: Prob. 1.26: Estimate how long it would take a runner at 10 km / hr to run from New York to California. Explain your solution thoroughly.
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RESPONSE --> Without taking into consideration stops for food, sleep, rest etc., it would take approximately 450 hrs to run. 2800 mi * (1.6 km/1 mi) * (1hr/10km) = 448 hrs, or 450 if all numbers are rounded to 2 significant figures. confidence assessment: 2
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22:59:02 It is about 3000 miles from coast to coast. A km is about .62 mile, so 3000 miles * 1 km / (.62 miles) = 5000 km, approximately. At 10 km / hr, the time required would be 5000 km / (10 km / hr) = 500 km / (km/hr) = 500 km * (hr / km) = 500 (km / km) * hr = 500 hr.
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RESPONSE --> ok self critique assessment: 3
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23:03:32 All Students: Estimate the number heartbeats in a lifetime. What assumptions did you make to estimate the number of heartbeats in a human lifetime, and how did you obtain your final result?
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RESPONSE --> (60 beats/min) * (60 min/hr) * (24 hr/day) * (365 days/yr) * (80 yrs/ lifetime) = 2,500,000,000 heartbeats/ lifetime Assumptions: heart beats an average of 60 beats/min a life time is 80 years confidence assessment: 2
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23:03:59 ** Typical assumptions: At 70 heartbeats per minute, with a lifetime of 80 years, we have 70 beats / minute * 60 minutes/hour * 24 hours / day * 365 days / year * 80 years = 3 billion, approximately. **
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RESPONSE --> ok self critique assessment: 3
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23:04:16 University Physics Students Only: Problem 1.52 (i.e., Chapter 1, Problem 52): Angle between -2i+6j and 2i - 3j. What angle did you obtain between the two vectors?
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RESPONSE --> I'm in Phy 201 confidence assessment: 3
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23:04:22 ** For the given vectors we have dot product =-2 * 2 + 6 * (-3) = -22 magnitude of first vector = sqrt( (-2)^2 + 6^2) = sqrt(40) magnitude of second vector = sqrt( 2^2 + (-3)^2 ) = sqrt(13) Since dot product = magnitude of 1 st vector * magnitude of 2d vector * cos(theta) we have cos(theta) = dot product / (magnitude of 1 st vector * magnitude of 2d vector) so that theta = arccos [ dot product / (magnitude of 1 st vector * magnitude of 2d vector) ] = arccos[ -22 / ( sqrt(40) * sqrt(13) ) ] = arccos ( -.965) = 164 degrees, approx.. **
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RESPONSE --> ok self critique assessment: 3
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23:04:52 Add comments on any surprises or insights you experienced as a result of this assignment.
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RESPONSE --> flow diagrams really are helpful self critique assessment: 3
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23:05:02 ** I had to get a little help from a friend on vectors, but now I think I understand them. They are not as difficult to deal with as I thought. **
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RESPONSE --> thats nice self critique assessment: 3
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