course Phy 201 ???????¦?T???@??assignment #005
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19:34:54 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 --> We find final velocity as follows: vf = vo + a`dt where final velocity is the sum of initial velocity and the product of acceleration and time interval. Now knowing final velocity we can solve for displacement as follows: `ds = (vf + vo)/2 * `dt where displacement is the product of average velocity and time interval.
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19:35:35 ** 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
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19:38:19 Describe the flow diagram we obtain for the situation in which we know v0, vf and `dt.
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RESPONSE --> Description of flow diagram knowing vo, vf & `dt: From vo and vf we calculate `dv. From `dv and `dt we calculate a. From vo and vf we calculate vAve. From vAve and 'dt we calculate `ds.
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19:38:56 ** 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
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19:44:59 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 --> I guessed (because I have absolutely no idea how far Ca is from NY and at the time no resources available to me to find out) that they're approximately 2,000 miles apart. Using this guestimate, I converted miles/hr to km/hr and solved for 10 km/hr as follows: 2,000 mi * (1.609 km/mi) = apprx. 3,200 km 3,200 km * (1 hr / 10 km) = apprx. 320 hours
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19:45:34 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
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19:53:28 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 --> Estimating lifetime to equal 80 years and heart rate to be 75 beats per minute, I solved as follows: 80 years * (365 days / year) * (24 hours / day) * (60 min / hour) = apprx. 4.2 * 10^7 min (75 beats / min) * (4.2 * 10^7 min) = apprx. 3.2 * 10^9 beats
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19:53:49 ** 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
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19:53:57 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 -->
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19:54:04 ** 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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19:54:14 Add comments on any surprises or insights you experienced as a result of this assignment.
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RESPONSE -->
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19:54:23 ** 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 -->
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19:54:24 ** 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 -->
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