Science & Mathematics - 14 October 2007

how many million (or billion) years ago did the precambrian era begin?

2007-10-14 13:03:33 · 3 answers · asked by indifferent 2 in Earth Sciences & Geology

1 Line L is tangent to the graph of y=x-(x^2/500)
on the graph, L crosses y axis at (0, 20)
point Q is on the both graph of y=x-(x^2/500) and the tangent line L.

(a) Find the x-coordinate of point Q.

(b) Write an equation for line l in slope-intercept form.

(c) Suppose the graph of y=x-(x^2/500) shown in the figure, where x and y are measured in feet, represents a hill.
There is a 50-foot tree growing vertically at the top of the hill. Does a spotlight at point P directed along line l
shine on any part of the tree? Show the work that leads to your conclusion.

**** and would you please be accurate and show details?? cuz i am not smart enough... :((****

2007-10-14 13:03:12 · 2 answers · asked by leonardo 1 in Mathematics

An automobile manufacturer can produce up to 300 cars per day. The profit made from the sale of these vehicles can be modeled by the function ... P(x)= -10x^2 + 1700x - 52,000

a) How many cars should be made and sold to maximize profit?

b) What is the maximum profit?

2007-10-14 13:02:17 · 1 answers · asked by Anonymous in Mathematics

1) A 2.05 g sample of a metal alloy is heated to 98.88°C. It is then dropped into 28.0 g water in a calorimeter. The water temperature rises from 19.73°C to 22.00°C. Calculate the specific heat of the alloy.

2) A piece of stainless steel (specific heat = 0.50 J/g°C) is taken from an oven at 168°C and immersed in 215 mL of water at 25.9°C. The water temperature rises to 42.4°C. What is the mass of the piece of steel?

2007-10-14 13:01:52 · 1 answers · asked by unknownanonymous999 2 in Chemistry

A horizontal force of 150 N is used to push a 36.0 kg packing crate a distance of 6.25 m on a rough horizontal surface. If the crate moves at constant speed, find each of the following.
(a) the work done by the 150 N force
I got 937.5 J
(b) the coefficient of kinetic friction between the crate and the surface
????HELP!!

2007-10-14 13:00:52 · 1 answers · asked by Anonymous in Physics

Help with this problem please?

2007-10-14 12:57:11 · 1 answers · asked by eclipsegt_01_03 2 in Mathematics

Ok, I'm doing a oral presentation on hurricanes and I need someone to tell me what's it like to be when there's a hurricane outside or you survived a hurricane, or if you lost someone and more stuff like that and if it's ok with you guys, get me some information that's really interresting about hurricanes.

Thanks alot :D

2007-10-14 12:56:00 · 10 answers · asked by babyyorangee21 2 in Weather

2007-10-14 12:55:14 · 2 answers · asked by Kelly 1 in Physics

2007-10-14 12:53:11 · 5 answers · asked by Anonymous in Biology

y = -x² + 6x -5.5
find the vertex and graph of

2007-10-14 12:52:49 · 1 answers · asked by true2b 1 in Mathematics

Gold has density of 19.3 103 kg/m3. What would the radius of a solid gold sphere have to be if the acceleration due to gravity at its surface is to be 9.81 m/s2? Check your answer against the radius of the Earth, which has a mean density of 5.5 103 kg/m3.
r = _____km???

2007-10-14 12:50:38 · 1 answers · asked by baron 2 in Physics

A 150 g bullet is fired from a rifle with a barrel of length of 65 cm. The bullet starts from rest at one end of the barrel and experiences a position-dependent force due to the expanding gas given by F(x) 15,000 + 10,000x - 25,000xsquared in Newtons with x in meters.
1. Calculate the work done on the bullet by this force over the length of the barrel.
2. Assuming that this is the only force doing work on the bullet (neglect friction) find the speed of the bullet as it leaves the rifle.
Please show all work so i can understand how to do the problem

2007-10-14 12:50:27 · 1 answers · asked by hawksup2 3 in Mathematics

A simple income tax schedule is shown.

Income Tax
up to $20,000 15% of income
More than $20,000 $3,000 + 28% of income in excess of $20,000

a. for what incomes is the tax at least 20% of total income?
b. for what incomes is the tax at most 25% of total income?
c.Tony's employer wants him to work overtime hours in December. If Tony does his, his income for the year will barely exceed $20,000. Tony is worried that, since the additional income will change his tax bracket, he will actually lose money that is, his additional taxes will exceed his added income, by working more hours. Are his fears justified?

2007-10-14 12:49:09 · 3 answers · asked by Ryoma Echizen 3 in Mathematics

I am developing a Prejudice Against Professors (PAP) scale. I've given the scale to 1000 students and found that they have a mean score on the scale of 26.5 with a standard deviation of 3.5. If Kara gets a score of 19.5 on this scale, fill in the blanks below so that her score would be equivalent in each case:
a. mean of X scores=100, s=15, X=__
b. mean of X scores=__, s=2, X=-9
c. mean of X scores=60, s=__, X=45
d. mean of X scores=10, s=20, X=__
e. mean of X scores=100, s=__, X=90

2007-10-14 12:47:53 · 1 answers · asked by Chien G 1 in Mathematics

what is the acceleration of a ball dropped? is it -9.81 or 9.81

2007-10-14 12:46:56 · 4 answers · asked by Desilicious 1 in Physics

2007-10-14 12:45:58 · 7 answers · asked by roberthinerman 1 in Engineering

i need help!
:)

2007-10-14 12:44:03 · 3 answers · asked by Anonymous in Mathematics

2007-10-14 12:43:00 · 2 answers · asked by naetashya p 1 in Medicine

A 450 kg autombile rounds a curve of radius 50 m at a constant speed. The roadway is banked at an angle of 25 degrees. If the automobile experiences a static frictional force of 815 N acting down the incline, determine the speed of the car. Please show how to do it now just the answer so i can learn how to get the answer.

2007-10-14 12:41:39 · 2 answers · asked by hawksup2 3 in Mathematics

Solve the equation log_x (8 )+ 2 log_2 (x) = 7

NOTE: the log_x 8 is actually log base x (8) and the 2 log_2 x is also acutally 2 log base 2 (x)...

Please show me your workings clearly....thanks a lot.

2007-10-14 12:41:26 · 1 answers · asked by Anonymous in Mathematics

A 10 g, bullet is fired into a 10 kg wood block that is at rest on a wood table. The block, with the bullet embedded, slides 5 cm across the table. What was the speed of the bullet?

( coefficients of static and kinetic friction are not given but from a table in the book wood on wood coefficient are:
static= 0.5
kinetic= 0.2
I thought that might help!)

This is question 38, from chapter 9 of book:
Physics for Scientist and Engineers, By Knight

2007-10-14 12:40:31 · 2 answers · asked by Anonymous in Physics

A 71 kg climber is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.83 and 0.65, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that friction forces are both at a maximum.

2007-10-14 12:39:17 · 1 answers · asked by lcbby 1 in Physics

Prove that this series:

cosx = (1 - (x^2/2!) + (x^4/4!) - (x^6/6!) + ...) = summation notation symbol (with n=0 on bottom and infinity on top) of (-1)^n x^(2n)/(2n)!

represents cosx for all "x".

2007-10-14 12:38:12 · 2 answers · asked by Anonymous in Mathematics

2007-10-14 12:38:06 · 2 answers · asked by Anonymous in Physics

?

2007-10-14 12:34:56 · 11 answers · asked by Anonymous in Mathematics

A 5.00 kg block is placed on top of a 12.0 kg block that rests on a frictionless table. The coefficient of static friction between the two blocks is 0.600. What is the maximum horizontal force that can be applied before the 5.00 kg block begins to slip relative to the 12.0 kg block, if the force is applied to (a) the more massive block and (b) the less massive block?

2007-10-14 12:34:21 · 2 answers · asked by tazk 1 in Physics

Differentiate In (4x + 5 / 2 - 3x) with respect to x.

Ans: 23 / (4x + 5) (2 - 3x)

Please show me your workings and explain...I need to understand...thank you

2007-10-14 12:33:58 · 3 answers · asked by ♪£yricảl♪ 4 in Mathematics

...At time t=2.8 hours the area of the circle is (to within .001) changing at a rate of what?

2007-10-14 12:33:33 · 2 answers · asked by eclipsegt_01_03 2 in Mathematics

I need to find the area of the shaded triangles in stage in for the Sierpinski triangle. I know the formula for the smallest number of white triangles in each stage (n) is 3^(n-1) but that's only the first half of the problem. Please help!

2007-10-14 12:32:34 · 2 answers · asked by Lillie 3 in Mathematics

Find the Taylor series for f(x) centered at the given value of "a". [Assume that "f" has a power series expansion. Do not show that Rn(x) -> 0].

1) f(x) = 1 + x + x^2, a=2

2) f(x) = 1/sqrt of x, a=9

show work plz..thanks!

2007-10-14 12:32:28 · 1 answers · asked by Anonymous in Mathematics