Math Help Please

Sorry guys, i know this isnt a homework forum or anythign, but i really need help with this thing.

Aite well just saying that i had an equation that was

h = height
t = time

h=-4.9t²+22.8t

1)How would i go about finding when the ball was at its maximum height?
2)And how would i go about finding out how long it was in the air for?

Fuck math...:thumbsdow

Wouldnt you need the velocity of the ball and/or the trajectory angle to use that equation?

You should learn derivables...
Anyways you acheive maximum height at 2.33 seconds. Replace that time for "t" and you get 26.52. Now your maximum height is during half the travel, so the duration in air equals to 2 times max height time which is 4.66

Hope you get your answer in time

Wouldnt you need the velocity of the ball and/or the trajectory angle to use that equation?

No.

You already know that the ball deccelerates and accelerates at gravity's constant for acceleration.
Given that you should be able to solve that equation easily enough.

You have to use other velocity equations in conjunction with the one given to resolve it though.

Heh im with you on this one KustmAce, i hate math.

oh yeh and Raz_Kaz thanks for you answer bud, but may i ask how you go to that, so i may use it for further questions and stuff, like i just found out a way to do it myself by completing the square, but would you be able to tell me your way.

Thanks for the help buddy

Ok I always went liek this,
h=-4.9t²+22.8t
let h=y and t=x
y=-4.9x²+22.8x (Now common factor)
y=x(-4.9x+22.8) (Now find the roots)
x=0 x=-4.9+22.8
And I can't remeber how the rest goes but basically you want to find the vertex of the parabola and the y value will be the optimal height and the x value will be the time it took to get there. (The total time in the air will be double the x value of the vertex since it is a midpoint). Sorry I couldn't help more but it's been a while and I sucked at it. Good luck.

Well GS, I'm not good at explaining but i'll give it a shot...
what your doing is derivables (something we're learning in grade 2 calculus here in Ontario)
Anyways here it goes....
h'=2(-4.9)+22.8, which is the drivable of your previous euation.
Complete it and you have h'=-9.8+22.8
Now you get a max or min when the derivable equals 0 so....0=-9.8t=22.8
Bring the 22.8 on the other side and you get -22.8=-9.8t
t=-22.8/-9.8....which t=2.33
Now you have the time when your going to have a max or min, so replace the value of "t" in the orginal equation
h=-4.9(2.33squared)+22.8(2.33)...And you get the value of h=26.52
Now the max or min of a projectile is in the middle, since you have the time where you reach that maximum or minimum, double it and you have the duration of the trajectory...


Hope thats clear enough

graphing calculator. The best $120 you'll ever spend.

/\ Cheap!!! :P...even though it works, what will you do when you don't have it? I don't like math but still...my Calculus teacher is a calculator, how many here can the the third root of sin 45 in their heads??? He can :lol2:

Too many numbers...head exploding.....

ahhhhhh sick thanks alot both of you guys, appreciate your help. This is the way i found out how to do it like 20 minutes ago, well i knew it before, but i didnt remember it all.

This is wat i did step by step,

h=-4.9t2+22.8t

Then i went ahead and completed the square which got me

h= -4.9 (t-4.65 + 5.405625 - 5.405625)
h= -4.9 (t-2.325)² + 26.4875625

and one of my friends told me that the height would be 26.4875625

At what height will the remnants of Zebrathree's head decelerate and start the descent back toward earth?

I NEVER decelerate! How dare you imply that I do!

LOL, let me work on that...but im going to need his head weight, initial velocity and more info :lol2:
But thats getting into physics not calculus




On a side note, GS, learn the damn derivables, so much easier, trust me...

On a side note, GS, learn the damn derivables, so much easier, trust me...


Or just type it into the calc... Thats easier, trust ME ;)

No, burn the paper.

Burn the paper.

Burrrrn the paaaapeer.

*Z3 cocks an eyebrow*

Trust ME.

/Manson hypno.

On a side note, GS, learn the damn derivables, so much easier, trust me...

be my personal tutor ;), heh yeh man i really gotta learn it your way, it seems to be easier. Hopefully i'll learn it as i go on, im only 16 heh

yea, so you have next year to learn it...have fun with that, it gets way more fun as you go along. (well depending on where you live)
dayna240sx, how lazy can you be??? :lol: jk
Not everyone has a graph calc, let him learn

heh i like in Ontario, Oakville to be exact, and yeh damnit dayna, let a youngun like me learn heh ;)

Yea, but i'm also in a french highschool, so our curricilum is a bit more advanced than yours ;)

actually when you take upper level math classes it is required you have a graphing calculator. I'm not lazy at all. I took senior level math as a sophomore in high school, and I've taken 4 higher level math classes as electives for my degree at college.... All those classes it was required that I have a graphing calculator. So, I'm not lazy, I just know the easier, faster way to figure things out.

ughhhhhhh frenchies.............


heh just playing man, i got nothign against french people, anyways i gotta get back to this shit, so i have all the answers allready done for my RAT tommrow.


THANKS for all your help guys
(apart from the ones that tried to say no too learning, ;) heh just playing, thanks to everyone )

On this subject can anyone do the derivable of y=ln6x+ln2x?
jk, just the hw im doing now, though id share

well dayna,
in my math class we also use graph calcs, but only to check if we got the right answer. Everything else is done the manual way...

well, have fun doing trig in your head :)

Damn, this whole thread is giving me a nasty headache.

I hate math with a passion. Luckily, Im done with it in HS!

w00t!

PS: Why are you doing math anyway? You not get summer break?

No dayna,
we have normal calcs, paper and pen. Useful tools they are :lol2: No, summer vacation doesnt start till after the 16th of June. But I got prom this weekend and im going to get fucking wasted

PS: Why are you doing math anyway? You not get summer break?


nah bud not yet, i cant wait though, just another 1 & 1/2 weeks and then im outta this hell hole for two months heh. Im looking to get a job and make some money and what not, so i literally cant wait to get school over and done with.


BTW: for all you people wondering this question was important to me, becuase its one of my final taks of the year, and is worth about 15% of my final mark. Not this question alone, but this is the first step in solving the final question.

anways thanks again for all your help guys.

Damn!! You get out this late? We got out May 21st.

heh yeh man, we definately get fucked over. Heh it'd be pretty sick if we got out on the 21'st since thats my birthday, that would be the best gift of the year, to get outta school for 2 months heh.

either way i cant wait until summer is here heh.

What the hell is a derivable?

Here's your other answer you wanted:

y = ln6x + ln2x
y' = 6/x + 2/x

easy stuff, the answer is 3.

What the hell is a derivable?

Here's your other answer you wanted:

y = ln6x + ln2x
y' = 6/x + 2/x
I already got it
y=ln6X+ln2X
y'=1/6X x 6+ 1/2X x 2
y'=1/X+1/X
y'=2/X

you want help with math? don't go to an automotive forum

Derivable must be another translation for Derivative.

I like derivatives... it's the antiderivatives/integrals that piss me off. Of course, after having taken about 3/4 of all the math courses offered at my Uni, I am kinda burnt out on math anyway. :redface:

lol, well in french it's "derivables" so i just pretty much tried to translate...yea pretty much what was said, still not any where near as hard as when i get into college