Prelim 2016 Maths Help Thread (3 Viewers)

[si2136]

Don't think this was the right place to post this since motion is HSC not prelim

Yeaaa

but it doesn't matter

 

[eyeseeyou]

eyeseeyou has come, as promised! Post up your questions

I'm here Shuuya

 

[eyeseeyou]

Okay someone help me or else I'm fucked

 

[parad0xica]

Okay someone help me or else I'm fucked

eyeseeyou can help you

 

[eyeseeyou]

eyeseeyou can help you

Thanks m8

 

[davidgoes4wce]

Do you have answers to Q1 , I just want to compare my answers? The questions seem pretty familiar from somewhere.

 

[eyeseeyou]

Do you have answers to Q1 , I just want to compare my answers? The questions seem pretty familiar from somewhere.

David for 1 the answer is a) x=t^2-4t+3
b)Some parabola lookign thing with 3 and -3
c) x=0
d)5m
e) 2m/s^2

 

[leehuan]

Okay here:

I just can't seem to get the jist of these questions

1.The velocity of a particle moving in a straight line is given by v=2t-4 ms. Initially the particle is 3m to the right of the origin O
a)find the displacement of the particle, x metres, at t second
b)Sketch the graph of x against t
c)Find the displacement at t=3
d)Find the distance travelled during the time interval 0≤t≤3
e)Find the acceleration of the particle at t=2

2. If v=t+lt-2l m/s, sketch the graph of v against t for 0≤t≤6, and hence find the distance covered during this time interval

3. A particle is moving in a straight line. It starts from a fixed point O on the line and at time t second its velocity v m/s is given by v=2cost
a. Find the first two times when the particle is at rest
b. find the distance travelled by the particle between these two lines
c. Find the acceleration particle when it is at rest

4. A particle moves in a straight line so that at any time t≥0 its velocity is given by v=1/(1+t)
a. if its distance from a fixed point O on the line is x, show that x=In(1+t), given that x=0 when t=0
b. Show that the particle is moving away from O as t increase
c. Find acceleration when t=0

5. An object falling from rest in air is suspended to an acceleration x (with 2 dots on top of x)=g-(v/k dash) where g and k are constants and v is the velocity and time t
a. Show that v=gk (1-(e^-(t/k)))
b. What is the greatest speed obtained?
c. What is the greatest distance travelled in the time t=k In 4

Why can't you just offer one question at a time when it pops up instead of throw so many at everyone and just causing mental exhaustion before you've even received any help??
________

For Q4,
a) given v=1/(1+t) direct integration yields that x = ln(1+t) + C
When t=0, x=0
So we have 0 = ln(1) + C
ln(1) = 0 so C = 0

So x = ln(1+t) as required

b) If the particle is moving away from O as t increases, then it should be that x is monotonic increasing. Hence, it suffices to show that v≥0 for all positive t

This is trivially true. 1/(1+t)>0 for all positive t is a true statement. (To see why, just sketch the graph.)

c) If v=1/(1+t) then x" = -1/(1+t)²
Just substitute t=0 to find the acceleration

(I randomly picked Q4 cause logs looked fun to play with, only to realise that it was a band 3-4 question. Are you sure you didn't attempt this in advance?)

 

[eyeseeyou]

Why can't you just offer one question at a time when it pops up instead of throw so many at everyone and just causing mental exhaustion before you've even received any help??
________

For Q4,
a) given v=1/(1+t) direct integration yields that x = ln(1+t) + C
When t=0, x=0
So we have 0 = ln(1) + C
ln(1) = 0 so C = 0

So x = ln(1+t) as required

b) If the particle is moving away from O as t increases, then it should be that x is monotonic increasing. Hence, it suffices to show that v≥0 for all positive t

This is trivially true. 1/(1+t)>0 for all positive t is a true statement. (To see why, just sketch the graph.)

c) If v=1/(1+t) then x" = -1/(1+t)²
Just substitute t=0 to find the acceleration

(I randomly picked Q4 cause logs looked fun to play with, only to realise that it was a band 3-4 question. Are you sure you didn't attempt this in advance?)

I tried to work it out but I'm just not there yet leehuan

 

[leehuan]

I tried to work it out but I'm just not there yet leehuan

What do you mean not there yet

 

[Shuuya]

Do you have answers to Q1 , I just want to compare my answers? The questions seem pretty familiar from somewhere.

Did you get the answers that eyeseeyou said were correct? Some of my answers are different

 

[eyeseeyou]

What do you mean not there yet

I mean I just can't seem to solve it no matter what I do

 

[eyeseeyou]

Did you get the answers that eyeseeyou said were correct? Some of my answers are different

what were thye Shuuya?

 

[eyeseeyou]

what were thye Shuuya?

Oh shit maybe I'm looking at the wrond answer sheet but idk wtf I'm doing lol

 

[Shuuya]

Oh shit maybe I'm looking at the wrond answer sheet but idk wtf I'm doing lol

Naah, most of them are the same

The parabola should have x intercepts (1,0) (3,0) and y intercept (0,3)?

 

[leehuan]

I mean I just can't seem to solve it no matter what I do

With regards to Q4, look at my answer and tell me where you got stuck please for my own reference sake

 

[eyeseeyou]

Naah, most of them are the same

The parabola should have x intercepts (1,0) (3,0) and y intercept (0,3)?

Graph it for me and show me it

 

[davidgoes4wce]

 

[eyeseeyou]

With regards to Q4, look at my answer and tell me where you got stuck please for my own reference sake

You got a right but for b it was a=-1 and for some reason I can't find C there

 

[eyeseeyou]

yeah but the parabola isn'tsupposed to cross into the negative side