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Please help- last Q in chapter- M2 :)

​I would really appreciate it if somebody would help me finish the M2 projectiles chapter.
https://6caf30cbcaf0c74dfdacf3d63c55c3d00fb8f0e6.googledrive.com/host/0B1ZiqBksUHNYMUk1VFNFeEZJY1U/CH1.pdf
So the first Question- (just to get started)...
Exercise B Q 10.- Did they make a mistake in part C? (they also give roots of velocity eqn below answer). I think they made a huge mistake :/
Thanks! :smile:
(edited 9 years ago)
Do it yourself

Show your working and proof of what youve done
Original post by schindlers list
Do it yourself

Show your working and proof of what youve done

omg I have. I did not get the answer of 42 which it is supposed to be.
Integral of velocity eqn is S=t3−6t2+5tS= t^{3} -6t^{2} +5t
I put in values for 4 and the root and then the integral from the root to 3. I got a really small answer... :/
If you look at the solution bank it gives incorrect roots (geogebra agrees) and in reality the velocity does change sign...
The question asks for distance travelled in the interval [3,4] - so it means you mod the negative integral value (for 1 of the integrals). Correct me if I'm wrong.
(edited 9 years ago)
bump
Original post by MathMeister
omg I have. I did not get the answer of 42 which it is supposed to be.
Integral of velocity eqn is S=t3−6t2+5tS= t^{3} -6t^{2} +5t
I put in values for 4 and the root and then the integral from the root to 3. I got a really small answer... :/
If you look at the solution bank it gives incorrect roots (geogebra agrees) and in reality the velocity does change sign...
The question asks for distance travelled in the interval [3,4] - so it means you mod the negative integral value (for 1 of the integrals). Correct me if I'm wrong.

No

Show the working so lying
Original post by schindlers list
No
Show the working so lying

:redface: I have kind of given lots of info/ working./proof I just wanna know if they are wrong or not! I cannot find that out :/ :smile:
bump... come on guys/gals
Original post by MathMeister
bump... come on guys/gals


I was trolling

I dont know none of these lol :smile:
Original post by schindlers list
I was trolling shodd of then off yeh pop
I dont know none of these lol :smile:

ha yah I know
twas why i was asking others lol
(edited 9 years ago)
Original post by MathMeister
ha yah I know
twas why i was asking others lol


It does seem like they've made a mistake.

43−(6×42)+20=64−96+20=−12≠−60 4^3-(6 \times 4^2)+20 = 64-96+20 = -12 \not= -60
Original post by ThatPerson
It does seem like they've made a mistake.

43−(6×42)+20=64−96+20=−12≠−60 4^3-(6 \times 4^2)+20 = 64-96+20 = -12 \not= -60

I do not know how to do it. Plz may somebody help me get the correct answer?
Original post by ThatPerson
It does seem like they've made a mistake.

43−(6×42)+20=64−96+20=−12≠−60 4^3-(6 \times 4^2)+20 = 64-96+20 = -12 \not= -60

Is the answer the integral of the velocity eqn from 4 to the root where v changes sign. plus the mod of the integral from the root to 3?
I got 2.256902162 metres ???
Original post by MathMeister
Is the answer the integral of the velocity eqn from 4 to the root where v changes sign. plus the mod of the integral from the root to 3?
I got 2.256902162 metres ???


I can't quite follow what you've written there but I believe the correct answer is 2.26m.
Original post by ThatPerson
I can't quite follow what you've written there but I believe the correct answer is 2.26m.

Ahhh ok :smile: Thanks I surely got it right then- our method then is correct :tongue:
Original post by ThatPerson
I can't quite follow what you've written there but I believe the correct answer is 2.26m.

still doesnt solve why one of my quadratics in another question ended in an imaginary number for T lol :tongue:
Correct eqn and everything cus it worked when changed into linear eqn haha

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