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#26 Help Me ! » Mechanics » 2008-02-25 02:22:36

EMPhillips1989
Replies: 12

hi
im a bit confused on the following question

when two particals a and b are projected vertically upwards from the same point one after another, with initial speed U.
if

is the time interval between the two projectiles where

find the time before the particals collide

does anyone know how to attempt this sort of question please help!!!!!

#27 Re: Help Me ! » calculus » 2008-02-19 06:34:53

EMPhillips1989

yes thats what i got thought it may have been more complex than that!

#28 Help Me ! » calculus » 2008-02-19 05:17:05

EMPhillips1989
Replies: 3


does anyone know how to evauate this integral?

#29 Re: Help Me ! » differentiation » 2008-02-19 03:47:44

EMPhillips1989

so far what i've done is:



now im a little lost as to what to do now

#30 Re: Help Me ! » differentiation » 2008-02-19 03:32:30

EMPhillips1989

what im trying to do is prove that

#31 Help Me ! » differentiation » 2008-02-18 06:52:28

EMPhillips1989
Replies: 4

the function

where
and

im trying to solve the second derivative of this function in terms of x and y

does anyone know whether im suppose to change to polar coordinates or can it be solved in this form??
im not sure how to convert this into polar form?
please help!!!

#32 Help Me ! » sequences » 2008-02-18 00:03:04

EMPhillips1989
Replies: 3

can anyone prove that

please help!!

#33 Help Me ! » proof by contradiction » 2008-02-17 22:15:52

EMPhillips1989
Replies: 1

let x be a real numer such that


and that for any n there is a natural number N such that

explain carefully what x must be

#34 Re: Help Me ! » Mechanics- Please help!!!! » 2008-02-16 05:57:31

EMPhillips1989

thank you very much that really helped me!!!

#35 Help Me ! » Mechanics- Please help!!!! » 2008-02-16 05:00:11

EMPhillips1989
Replies: 2

so ive been having a problem with the following question:

A car initially at rest accelerates at a rate


determine the distance when the car comes to a hault.

so this is my attempt at answering the question

As



Integrating this with respect to time gives:
where c is a constant
At x=0, t=0, so c=0
As


Integrating this again with respect to time gives:
where d is a constant
At x=0, t=0,

which gives:

which gives the position in terms of time

For this sort of question am I supposed to find an exact distance in metres? The questions goes on to ask how long the cars cars been travelling and the maximum speed attained by the car.
Can anyone give me some idea as to what to do next if this method is correct
Please help!!!

#36 Help Me ! » probability » 2008-02-14 02:48:05

EMPhillips1989
Replies: 2

does anyone know how i would answer a question like the following?

Let X be the outcome when a fair die is rolled once. Before the die is rolled you are offered either a guarenteed amount:

  pounds
or a gamble of

what is the best strategy to accept the guaranteed amount or gamble?

#37 Re: Help Me ! » integration » 2008-02-12 09:57:56

EMPhillips1989

oh i should have known to do that!rolleyes

thankyou!

#38 Help Me ! » integration » 2008-02-12 08:42:33

EMPhillips1989
Replies: 2

does anyone know a simple way of doing this???

#39 Help Me ! » sequences » 2008-02-11 09:58:02

EMPhillips1989
Replies: 4

hey can anyone help me prove that the sequence

converges to 2??

any advise would be much appreciated!!!

#40 Help Me ! » mechanics please help!!!! » 2008-02-09 04:34:41

EMPhillips1989
Replies: 1

hey can anyone help me out i've attempted to complete a question for revision purposes but i'm not sure what i've done is correct. i'm new to mechanics and was wondering if anyone could possibly point me in the right line

The question is:
A car accelerates from rest to 28m/s in 10 seconds.
by working from first principles find the cars acceleration, and the distance travelled in this time in metres.

My attempt at solving:
the car moves in direction x at constant speed u. after a time, t the car will be at the position:


since the car is acelerating, its speed is no longer constant and now depends on time.  u=u(t)
since velocity is the rate of change of position with time
      [1]
and acceleration is the rate of change of velocity with time
      [2]
intergrating w.r.t time gives:
where c is a constant
since car started at rest when t=0, u=0 therefore c=0

which leaves


To find the acceleration i did:


Now to find the distance travelled in this time i did:


from [1]

integrating this w.r.t time gives:
where d is a constant
when t=0 x=0, therefore d=0
so we get:

using the information given and a=2.8m/s^2

x=140 metres

#41 Help Me ! » vector equations » 2008-02-09 03:13:53

EMPhillips1989
Replies: 1

does anyone know why the vector equations

and
both describe a straight line in the direction of c through the point d??

#42 Help Me ! » series » 2008-02-07 23:25:55

EMPhillips1989
Replies: 3


does anyone know if this series converges or diverges?
What test for convergence would be best to use for this type of series??

#43 Re: Help Me ! » please help » 2008-02-04 22:36:52

EMPhillips1989

so i tried adding them together this way and i seem to get the right answer im just not sure if my method is correct
i got

#44 Re: Help Me ! » please help » 2008-02-04 09:41:03

EMPhillips1989

When i use the triangle inequality i seem to get

when i surely want it to be 
for
to be truecan you see where i've gone wrong????

#45 Help Me ! » please help » 2008-02-04 08:23:42

EMPhillips1989
Replies: 5

Let


and a,b,c be real numbers such that
and

show that

#46 Help Me ! » convergent sequences » 2008-02-04 08:09:17

EMPhillips1989
Replies: 3

hey can anyone help me prove that the sequence {an} given by


converges to 0
this is clearly obvious i just dont see how to apply a proof can anyone please help???

#47 Re: Help Me ! » Stats please help » 2008-02-01 08:13:28

EMPhillips1989

Thankyou very much you've really helped me understand the question alot better!!!!!

#48 Re: Help Me ! » Probability » 2008-02-01 07:20:14

EMPhillips1989

yes but im not sure it can be done as easily as there is a greater percentage as 80 out of 100 students were more satisfied with book C, do you see where im coming from??

#49 Help Me ! » Stats please help » 2008-02-01 06:08:32

EMPhillips1989
Replies: 4

A family  that owns two cars is selected at random
Let A={the older car is a BMW}    B={the newer car is a BMW}
If P(A)=0.8   P(B)=0.6  P(AnB)=0.4

does anyone know how i would go about answering the following questions??

compute:
1) the probability that the newer car is a BMW given that the older car is a BMW??
2) the probability that the older car is a BMW given that the newer car is NOT a BMW???

i think it's the phrasing of the question which im getting confused on if anyone could please help i will be very grateful xxxx

#50 Help Me ! » Probability » 2008-02-01 05:56:41

EMPhillips1989
Replies: 3

In a school of 500 students, each were given one of three revision books
250 were given book A
150 were given book B
100 were given book C

A survey said that:
100 were satisfied with book A
75 were satisfied with book B
80 were satisfied with book C

if a student is selected at random and is satisfied with her book, which book A B or C are they most likely to have used?
which book is the student least likely to have used???

does anyone know how i would go about answering a question like this any help will be very much appreciated!!!:D

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