Homework Help: Vertical and horizontal components,physics As level help :(

1. May 22, 2017

Maryam9

1. The problem statement, all variables and given/known data
This is paper from june 2016 , the link below;
http://qualifications.pearson.com/c...2013/Exam materials/WPH01_01_que_20160524.pdf
Can someone pleeeeeze explain how to solve question 15 part B AND queation 16 part B .
I have an exam tmrw so plz plz if someone could explain this to me

2. Relevant equations
How do write the answer in part b of Q16
How to solve the question?

3. The attempt at a solution
for question 15 I tried using the tension formula T=mg+ma but dont know how to subtitue quantities in it
for question 16 I dont understand what the question is asking about angles , all I could understand that forces cancel out now if its right or no idk but idk how to write the answer :(

2. May 22, 2017

BvU

Hi Maryam,

At the risk of being severely punished by our good mentors (answering is forbidden in PF, we are only allowed to help according to the rules ) - but heck, damsels in distress....

For 15a you may assume the whole lot is just hanging: no acceleration. There's only one fundamental difference between the fly FBD and that for the spider: there is a T1 pulling down. Once you have the FBDs you also have the equations for equilibrium (= hanging still).
Quantities are the givens (all in the form of symbols).

But you appear to ask about 15b: They give T1 and you will need to solve TWO equations of the type T=mg+ma : one for the fly and one for the spider. Look at the FBDs and write them down (in terms of the symbols).

For 16: You solved a) ? For b) you could look at T as a function of $\theta$ Or you could look at the horizontal component T$\sin\theta$ because that is what is pulling the pole tips towards each other.

3. May 22, 2017

Maryam9

Aww thanks !
What does FBD mean ?? And in question 15 they asked for the acceleration not tension , How do I get that??
And question 16 I was asking about part b , Idk how to write the answer cuz I dont understand it

4. May 22, 2017

BvU

Free body diagram

T2 - mflyg = ma for the fly
T1 - T2 - mspiderg = ma for the spider.

a is the same for both (The distance between them does not change). Eliminate T2 and there you are !

16: if $\theta$ increases, the horizontal components of T decrease, so the poles are not pulled together so hard any more. The vertical components remain the same.

5. May 22, 2017

Maryam9

ooh! ok Thank u so much :)

6. May 22, 2017

BvU

You're welcome. Good luck with the test.