Jenifer S

My power adapter broke and I have another one that fits.

The original:

Input: 100-240V AC 50-60Hz

Output: 12V DC 1.8A

The other one:

Input: 100-240V AC 50/60Hz

Output: 12V DC 1000mA

I remember reading somewhere that output is important..., can anyone confirm this so I don't burn my house down by accident?

Here's the question: 34.5 m length of copper wire at 20 degrees celcius has radius of 0.25nm. If potential difference of 9 V applied across length. The current in the wire is 3.0 A.

The questions asks to find current if wire is heated from 20 - 30 degree celcius.

I know that the equation I am to use is R = R(1 + alpha (30-20 degrees)

The numerical value the answers uses for alpha is 3.9X10^-3 C ...

where is this value coming from???

There are two word problems in the text that I can't figure out!

First one says a it costs a company $8000 to produce one bike and fixed costs are $20,000/week. When company produces 100 bikes it sells them at $15,000. Sale records indiciate that if price increases by $700 the sales will drop by 10% and vice versa. Assume the relationship between price and number sold is linear.

Using x for number of bikes, and p for price, find profit function P(x) and the number of bikes that will maximize profit.

I can't figure out the profit function to start off...

Hello all!

I'm doing some chain rule work with derivatives and I understand the rule well enough, but I KEEP getting stuck with the simplifying.

For example, I get an equation down to: [2/3(5x^4 - 2x)^(-1/3)] (20x^3 - 2)

The answer is 4(10x^3 - 1) / (3^3[sqrt(5x^4 - 2x)]

I realize this equation looks complicated so Ive taken a picture an added it here: http://imgur.com/inbhEZH

thanks!

I understand the basic rules of differentiation for the most part (product, quotient, chain rule, exponent rule etc). But I'm stuck on the following derivatives (most of them involve e, ln or sin and cos. I'm not sure I understand how to differentiate those)...

y = sqrt(3x)

z = w^2(sin[cos w])

s = e^(e^r)

y = xe^(3x) / x^2+x+1

d = ln (x^2+1/x^2-1)

I can't find any examples of this in the text but my prof. was going through some complicated examples of derivatives last class and I'm stuck on a few of them... any help would be appreciated!

1) y = sqrt(3x) ------------------- (I solved this to get dy/dx = sqrt(3x)/2x )

2) a = e^(2t+1) ------------------- (which I believe is just the same... as the rule (e^x)' = e^x)

3) z = w^2(sin[cos w])

4) s = e^(e^r) ------------------ (would this also just be the same? ds/dr = e^(e^r)?)

5) y = xe^(3x) / x^2+x+1

6) d = ln (x^2+1/x^2-1)

I think If I get these figured out I should have no problem with the second order derivatives or other questions.

I'm stuck on this even question in the text and there are only answers provided for the odd ones..

It asks to create a non-trivial function following the given instructions (no piece-wise functions)

b) A function that is continuous on the interval x ∈ [-3,inifity)

(a) asked for a function that is not a polynomial, and is continuous for all Real values of x and I answered x^1/5 so I think I answered that one correctly.

So the question says that a company has determined when a% of it's capacity is being used, the cost function in $100,000s is. C(x) = (8x^2 - 636x - 320)/(x^2 - 68x - 960)

The company usually runs at about 80% capacity.

1) if the company runs at 50% capacity, what is it's cost?

2) if 80% capacity is the normal capacity, what is the company's usual cost?

I'm not sure what Information I need to solve this. Can anyone help me out at all? Thank you.

I just need a bit of clarification here. I'm being asked to make up non-trivial funcitons f(x) to fit the requirements:

a) lim x->3 f(x) = 2 and f(3) exists.

The answer says it can be any function such that f(3) = 2. Would the function x-1 satisfy this??

Write ln[(2x-1)/((x^2)(x+5)^6)] as a sum or difference of logarithms simplified as far as possible.

This is part of the review portion we are responsible for and I have no idea how to even begin. Can anyone help me solve this??

on a review sheet, I'm asked to find the domain and range of f(x) = e^(x-3)

Can someone please explain how I go about doing this?

Thank you :)

actually it's solving for V1...

I have gotten the equation to this: .5km/V1 + 3.5km/2(V1) = .25 hr

I'm solving for V1 and the answer is V1 = 9.00km/hr

how do you get to this answer? I must be doing thinsg out of order...

What type of reaction occurs when aspiring is formed by reacting salicylic acid with acetic acid?

(Here is a picture but NOTE: the top CH3 is missing from the picture!!)

Can anyone help me name this?

http://imgur.com/VFd5E

- totally random fashion

- molecules aligned with long axes tilted with repsect to line perp. to he plane in which they're stacked

- molecules aligned along their long axes with no ordering repect to the ends (this is what I think is the answer)

- moles arranged in sheets - long axes parllel and ends aligned

- disk-shaped molecules are aligned through stakcing of disks in layers.

I have both the question and answer but I'm not sure how it's gotten. The question says: "It is estimated only 1/50 parrots captured for use as pets will survive. During one day, 700 parrots are captured. What is the expected number of survivors (which I know, is 700*1/50 = 14). What is the probability that at most, 10 birds will survive?

The answer says that using poisson approximation P(X</=10) = 0.176

Does anyone understand how that was gotten?

I'm doing physics and i'm stuck with solving for t in this equation.

(0.100m/s) t = (2.0m/s) (t-120sec) + .2m

I can't figure out how to isolate t but the answer is apparently 1.3x10^2s

A man needs to catch a train travelling 30km/hr. His horse is able to accelerate from rest at 4.0m/s^2, how long is needed for him to catch the train is he waited 2 full seconds after train passed before he started the chase?

I know the answer is 5.64s but I do NOT understand what do after you convert 30km/hr to m/s (which I got 108m/s.)

I have the answers for the question but not the route to them and I'm stuck..

'You immediately slam you brake after a telephone pole suddenly appears in the middle of your lane. Your car skids 62.4 meters in 4.20 seconds. If the acceleration from your brakes was -5.60m/s^2,

how was fast were you going before you hit the pole? (Ans: 26.2(2)m/s

How fast were you going when you hit it? (Ans: 3.10 m/s or ~11km/hr)

Hello! I have a question in my text book asking me to perform dimensional analysis on each one asking which are correct. I know the answer is that all three are correct but I don't understand how to do it. When I tried I must have been doing something wrong because I can't get any of them to work out.

1) 1/2mv^2 = 1/2mv(initial) + sqrt(mgh)

2) v = v(initial) + at^2

3) ma = v^2