I Suck at a SHM and need help (1 Viewer)

[Kingportable]

Ok so i read all the notes, memorised the formulas, looked at videos on maths online and listened to the teacher. I open the first question and was dumbfounded.

EXERCISE 25 (C), 3 UNIT MATHEMATICS JOHN FITZPATRICK HSC TEXT BOOK.
1. The equation of motion of a particle moving with simple harmonic motion is x'' (x double dot/aceleration) =-9x
Find its period, amplitude and greatest speed given that.

i) x=0, x'=2 when t=0
ii) x=2, x'=2 when t=0

*Please be very annotative

 

[Alkenes]

Bro my teacher use fitzpatrick for 3 unit....I don't like the book...most of the questions ain't exam style questions....i used other books and resources...
in a recent class test, I got 95% while the rest of the class got high 70s....

And what you don't understand in SHM? It is 'simple' lol

 

[Alkenes]

For your question, find x dot and x displacement by integration...sub in the values given

 

[Kingportable]

I agree John Fitzpatrick 3U does suck, my teacher wonders why no one finishes all the question in our class or the class that graduated last year.

 

[Alkenes]

You don't have to do every single question

I agree John Fitzpatrick 3U does suck, my teacher wonders why no one finishes all the question in our class or the class that graduated last year.

 

[Kingportable]

Lol anyways both ways i am a dumb ass and am still lost.
From looking through the book's example i some how got to...

n=4
asin(alpha) = 0
2acos(alpha) = 2

*since x=0 and x'=2
*apparently x'=2acos(2t+alpha)

 

[Kingportable]

If you go to Parramatta Library for Meat-2 on the 1st day - I can explain SHM to you. You don't have to be part of the official Meat-2. Just turn up and ask for me.

Drogonski bro i am broke haha.

 

[Alkenes]

LOL

Drogonski bro i am broke haha.

 

[Alkenes]

Your avatar is awesome...i keep refreshing my page LOL

 

[Drongoski]

Drogonski bro i am broke haha.

Don't worry. It turns out that I cannot do it as the Library will be too crowded on the day. So sorry I have to withdraw the (free) offer.

 

[iampeterr]

EXERCISE 25 (C), 3 UNIT MATHEMATICS JOHN FITZPATRICK HSC TEXT BOOK.
1. The equation of motion of a particle moving with simple harmonic motion is x'' (x double dot/aceleration) =-9x
Find its period, amplitude and greatest speed given that.

i) x=0, x'=2 when t=0

Acceleration = -9x in terms of (-n²x)
Period = 2pi / n
period = 2pi / 3 = 2/3 pi/sec

Amplitude: (EP - C) Endpoint - centre
Endpoints are when V = 0
So to get V, we need to integrate Acceleration.

d(1/2v²)/dx = ∫ -9x
d(1/2v²) = ∫ -9x dx
1/2v² = -9/2 x² + C
x=0, x'=2 when t=0
1/2(2)² = 0 + C
therefore, C = 2

1/2V² = -9/2 x² + 2
V² = -9x² + 4
To find end points, when velocity = 0
-9x² + 4 = 0
9x² = 4
x = +- 2 / 3

Therefore the end points are 2/3 or -2/3
Amplitude = EP - C
to find centre, take the average of them two.
therefore amplitude = 2 / 3

Max speed occur at origion, so when x = 0

V² = -9x² + 4
V² = 4
therefore v = 2m/s

 

[Kingportable]

Sweet thanks iampeter, don't wana be a bother. But this thing with 1/2v^2 has really been annoying me. I think i must have missed one of the classes.

 

[iampeterr]

any time
just know when you need to find velocity and you're given acceleration in terms of x, you can use d(1/2v^2)/dx

 

[Alkenes]

or we could use v.dv/dx

any time
just know when you need to find velocity and you're given acceleration in terms of x, you can use d(1/2v^2)/dx

 

[rainy_morning]

Bro my teacher use fitzpatrick for 3 unit....I don't like the book...most of the questions ain't exam style questions....i used other books and resources...
in a recent class test, I got 95% while the rest of the class got high 70s....

And what you don't understand in SHM? It is 'simple' lol

Hi, can you tell me which books u used to study 3u.

 

[maths lover]

Acceleration = -9x in terms of (-n²x)
Period = 2pi / n
period = 2pi / 3 = 2/3 pi/sec

Amplitude: (EP - C) Endpoint - centre
Endpoints are when V = 0
So to get V, we need to integrate Acceleration.

d(1/2v²)/dx = ∫ -9x
d(1/2v²) = ∫ -9x dx
1/2v² = -9/2 x² + C
x=0, x'=2 when t=0
1/2(2)² = 0 + C
therefore, C = 2

1/2V² = -9/2 x² + 2
V² = -9x² + 4
To find end points, when velocity = 0
-9x² + 4 = 0
9x² = 4
x = +- 2 / 3

Therefore the end points are 2/3 or -2/3
Amplitude = EP - C
to find centre, take the average of them two.
therefore amplitude = 2 / 3

Max speed occur at origion, so when x = 0

V² = -9x² + 4
V² = 4
therefore v = 2m/s

allot of unnecessary working out. we know that maximum velocity is achieved at the center when acceleration=0.
therefore using the formula v max=nA
2=3*A, therefore a=2/3.
as mentioned before max velocity is going to be 2. if you want me to prove the formula i used i can.

 

[Alkenes]

I still 'use' em coz im sitting HSC this year lol
I have got like more than 10 books for 3 unit (no jks)
SOme of em' are txtbooks, questions by topics, leading edge, um excel, revisions and study guides...
I use all of em'
AND of course PAST PAPERS!!

Hi, can you tell me which books u used to study 3u.

 

[Alkenes]

allot of unnecessary working out. we know that maximum velocity is achieved at the center when acceleration=0.
therefore using the formula v max=nA
2=3*A, therefore a=2/3.
as mentioned before max velocity is going to be 2. if +1you want me to prove the formula i used i can.

+1

 

[maths lover]

+1

well using this formula v^2=n^2(A^2-x^2), do i have to prove this as well?. firstly we know due to the definition of simple harmonic that acceleration=0 at the center, then -9x=0, therefore x=0. subbing in x=0 into the equation we get the required result. we also know that since acceleration is always opposing velocity then when acceleration=0velocity is subsequently a maximum.