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#1376 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-23 00:28:53

Okay, thank you very much. I have some more but I will post them later. Actually, here are some vector calculus questions:

Determine if the vector field f(x, y,z)= x yzi+xzj+x yk has a potential in R3

I am getting that it does not have the potential.

#1377 Re: Puzzles and Games » Can you suggest six names of great mathematicians quickly? » 2013-05-23 00:24:27

Hi; that's great. But unfortunately, I do not understand what you mean by CGPA and A1. I though marking was out of 500.

#1378 Re: Puzzles and Games » Entanglement » 2013-05-22 01:52:02

Phronister, is the only thing you do with your life puzzles?

#1379 Re: Puzzles and Games » Can you suggest six names of great mathematicians quickly? » 2013-05-22 01:47:34

Agnishom, how did your exams go? You were supposed to get your results a couple of weeks. ago, weren't you?

#1380 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 01:41:58

Oh, okay. Thank-you. The second one is a bit more complicated.

#1381 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 01:37:42

25m is 82 feet so did you simply approximate something?

#1382 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 01:13:57

Well, the units in the problem were feet, and 9.81 is approximately 32 feet. Also, "Similar to the problem in post 8. ground level will be position 0, up will be the positive direction and time t=0 will be the instant when Fred first throws the ball. The acceleration due to gravity will be a = -32."

#1383 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 01:05:44

Similar to the problem in post 8. ground level will be position 0, up will be the positive direction and time t=0 will be the instant when Fred first throws the ball. The acceleration due to gravity will be a = -32. Thus dv/dt = -32, so that v(t) = -32 + C. The problem does not give any information about the velocity of the ball at any time so I use v0 to represent initial velocity. AT time t = 0, I get v(t) = -32t + v0. So, as v(t) = dr/dt, y(t) = integral (-32t + v0)dt = -16t + v0t + C.

#1384 Re: Puzzles and Games » Chocolate! » 2013-05-22 00:53:58

Yes, but assuming they start with 2, take one (half of two) and return one immediately. That probably is not the case.

#1385 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 00:52:38

I get y(t) = Integral (-32t + v subscript 0)dt = -16t^2 + v subscript 0 t + C

So y(t) = -16t^2 + v0t   (o = subscript)

So 0 = -16 * 5^2 + initial velocity * 5 = -400 + 5 (initial velocity) = -400 + 5 initial velocity

Solving gives us V0 = initial velocity = 80 ft / second

#1386 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 00:44:50

Hi Stefy; for which question are you getting that?

#1387 Re: Puzzles and Games » Chocolate! » 2013-05-22 00:43:39

Well yes, that seems too easy if they take one and return one.

#1388 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 00:42:01

One more: Junita is standing on the roof of a building 192 feet tall and throws a ball up in to the air with an initial speed of 64 feet / second.

(a) Find formula for velocity and position of ball at a later time.  I get v(t) = -32t + 64 And for position: y(t) = -16t^2 + 64t +192

(b) How high does the ball go? I am getting 256 feet,

(c) When does the ball hit the ground? I think this is probably wrong, but I am getting 6 seconds.

Thank-you in advance.

#1389 Re: Puzzles and Games » Chocolate! » 2013-05-22 00:34:33

It says "each, in turn" thus I presume that they return one chocolate bar immediately after taking the toll.

#1390 Re: Help Me ! » Single-var Calculus (and otherwise) » 2013-05-22 00:33:07

Hi; few other simple problems. Fred is standing on the ground and throws a ball up in to the air. He observes that it falls back down to the ground after 5 seconds. What was the initial velocity of the ball? I get 0  =  -400 + 5V subscript 0 Thus initial velocity = 80ft / s

#1392 Re: Help Me ! » Parallelism » 2013-05-16 03:09:28

True... Is it actually accredited? There is a possibility that the whole thing is a ploy. That, or the US education system is corrupted.

#1393 Re: Help Me ! » Parallelism » 2013-05-16 03:03:37

I saw some of zee's posts before. The course administrator's don't seem to be too official though.

#1394 Re: Help Me ! » Parallelism » 2013-05-16 02:57:59

Well, they look like grade 7-8 level questions. Maybe just for practice?

#1395 Re: Help Me ! » Parallelism » 2013-05-16 02:55:31

Bob, I do not understand questions 8,9,10 and 11. Oh...now I see your older post. I thought I was just being stupid.

#1396 Re: Help Me ! » Parallelism » 2013-05-16 02:45:46

3 is incorrect as two interior angles on the same side of the transversal are supplementary. Thus, 3 should be yes. 4 also should be yes by the same rule. Question 8 is wrongly typed as Angle 7 should equal angle 3. Thus, 9, 10 and 11 are wrong questions.

#1397 Re: Help Me ! » Parallelism » 2013-05-16 00:43:13

1 is right by TPT-Z rule.

#1398 Re: Dark Discussions at Cafe Infinity » A heady experience. » 2013-05-16 00:19:34

I thought I saw this titled "Using her head"....

#1399 Re: Help Me ! » Power of 2.2 ? » 2013-05-15 01:06:09

Hi; It should be around 0.82

#1400 Re: Help Me ! » Power of 2.2 ? » 2013-05-15 00:55:44

That depends on the calculator. Usually you type 0.9176 and then press y^x and then 2.2

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