DE: quick help

Theirs just a few things that regularly pop up in DE exams that i could really use help understanding

1. When a v randomly appears in newtons 2nd law next to the acceleration and mass like in question 2 (i) of this paper.

http://www.mei.org.uk/files/papers/de_june_2012.pdf

2. When it says y is bounded as x tends to infinity i don't know how you would use this information, like in question 1 (ii) of this paper.

http://www.ocr.org.uk/Images/144670-question-paper-unit-4758-01-differential-equations.pdf

Any help would be greatly appreciated :smile:

Reply 1

BabyMaths

Original post by Mrbrian

Theirs just a few things that regularly pop up in DE exams that i could really use help understanding

1. When a v randomly appears in newtons 2nd law next to the acceleration and mass like in question 2 (i) of this paper.

http://www.mei.org.uk/files/papers/de_june_2012.pdf

a=\frac{dv}{dt}=\frac{dx}{dt} \frac{dv}{dx} =v \frac{dv}{dx}

As for your other question, could you post your general solution? Without looking at the question I'd say that if it's bounded certain constants will need to be zero.

Reply 2

brianeverit

9

Original post by Mrbrian

Theirs just a few things that regularly pop up in DE exams that i could really use help understanding

1. When a v randomly appears in newtons 2nd law next to the acceleration and mass like in question 2 (i) of this paper.

http://www.mei.org.uk/files/papers/de_june_2012.pdf

2. When it says y is bounded as x tends to infinity i don't know how you would use this information, like in question 1 (ii) of this paper.

http://www.ocr.org.uk/Images/144670-question-paper-unit-4758-01-differential-equations.pdf

Any help would be greatly appreciated :smile: