course phy 201
......!!!!!!!!...................................
21:57:06 Intro Prob 6 Intro Prob 6 How do you find final velocity and displacement given initial velocity, acceleration and time interval?
......!!!!!!!!...................................
RESPONSE --> Acceleration equals the change in velocity divided by the change in time a= 'dv/'dt so if you multiply the average acceleration time the change in time you get the change in veolcity. The change in velocity and then be used to find the final velocity. The final velcoity equals final velcoity minus the initla velocity. So by adding the initial velocity plus the change in velocity you get the final velocity. You then can solve for the average velcoity which is the initial plus the final velcotiy divided by two. Once you have the average velocity you can find the displacement by multiplying the change in time by the average velocity.
.................................................
......!!!!!!!!...................................
21:57:36 ** 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**
......!!!!!!!!...................................
RESPONSE --> right
.................................................
......!!!!!!!!...................................
21:58:27 Describe the flow diagram we obtain for the situation in which we know v0, vf and `dt.
......!!!!!!!!...................................
RESPONSE --> vo vf and 'dt would be on top then the next level would be aAve = (vf-vo)/2
.................................................
......!!!!!!!!...................................
21:59:14 ** 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. **
......!!!!!!!!...................................
RESPONSE --> I didn't know that it was suppose to just be the vAve not the aAve
.................................................
......!!!!!!!!...................................
22:00:40 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.
......!!!!!!!!...................................
RESPONSE --> How far is it across country?
.................................................
......!!!!!!!!...................................
22:03:47 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.
......!!!!!!!!...................................
RESPONSE --> Ok, so it is about 3000 mile across the country so 1km = 0.6214mi.. to find km you would divide 3000mi/0.6214mi = 4828km = 5000km then 5000 km / 10 km/hr = 500km/hr
.................................................
......!!!!!!!!...................................
22:07:36 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?
......!!!!!!!!...................................
RESPONSE --> You would have to assume that the heart rate is constant all the time. Say you had 60 beats a minute. 86400 beats per day. So for a year your heat would beat 31536000beats and if you lived till you were 80 then you would have 2522880000 beats.
.................................................
......!!!!!!!!...................................
22:07:47 ** 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. **
......!!!!!!!!...................................
RESPONSE --> right
.................................................
......!!!!!!!!...................................
22:07:53 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?
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
......!!!!!!!!...................................
22:07:58 ** 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.. **
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
......!!!!!!!!...................................
22:08:07 Add comments on any surprises or insights you experienced as a result of this assignment.
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
......!!!!!!!!...................................
22:08:15 ** 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. **
......!!!!!!!!...................................
RESPONSE --> ok
.................................................
"