Mathematics: Post your doubts here!

[Thought blocker]

Hi guys,

How is your math preparation going on? It's almost 3.5 months from your CIEs. How confident are you about 9709? ^_^

 

[Mushraf altaf]

Can someone help me with this?
I'm stuck on (ii)
I know we have to take moments about B. I don't know how find the distance of the center of mass of the triangle PQR.

 

[Alis alis]

 

[Alis alis]

 

[Jane_Kim]

Can anyone solve this? This is Mechanics Question 42 MayJune
2017... PLSS ANYONE!!!

 

[Hamnah Zahoor]

Can anyone solve this? This is Mechanics Question 42 OCTNOV 2018... PLSS ANYONE!!!

Question is from may June 2017 42

 

[Jane_Kim]

Question is from may June 2017 42

View attachment 64467

You are the best!!! yay I get it now!

 

[Jane_Kim]

what about this one?? What is the difference between this and the previous one?? I mean, it's kinda different and it confuses me...

 

[Jane_Kim]

This question is from 43 MayJune 2017...

 

[Hamnah Zahoor]

what about this one?? What is the difference between this and the previous one?? I mean, it's kinda different and it confuses me...

 

[Jane_Kim]

Can anyone help me with 3 ii) Its quite confusing...

 

[Hamnah Zahoor]

Can anyone help me with 3 ii) Its quite confusing...

what's the year of this question?

 

[Jane_Kim]

2017 Oct Nov paper 41

 

[sukasukinya]

Hi! Help me. Can someone explain to me for 7 (iii), why the answer in the mark scheme is the radius of 5 instead of 4?

 

[Thought blocker]

Hi! Help me. Can someone explain to me for 7 (iii), why the answer in the mark scheme is the radius of 5 instead of 4?

Printing error.

 

[Thought blocker]

Can anyone help me with 3 ii) Its quite confusing...

Using Work Energy Principle,

1. Let the starting point be A and the end point be C.

2. List down Energies and Work at point A and C

Point A:
Ep = 0 J
Ek = 1/2 × 840 × 14^2 = 82320 J
Work done against resistive force = 0 J

Point B:
Height from the ground = 8sin30 - 10sin20 = 0.58m
Ep = 840 × 10 × 0.58 = 4872 J
Ek = 1/2 × 840 × v^2
Work done against resistive force = from part i we got it as 11520 J

3. Use the work - energy equation and solve for v

Point A = Point B

82320 = 4872 + 420v^2 + 11520

Thus, v = 12.5 m/s (3sf)

 

[KashishV]

HI guys, so I wrote my AS level pure math 1 paper today and it was easy but I couldn't get a 6 marks question right :'((
they gave: y= [(x^3+x^2)]^0.5
and in the question, the very first thing we had to do was differentiate it. Now I'm usually good at differentiation. I can do the product rule, quotient rule and chain rule even. However I had this assumption, god knows why that in AS level at least, we can only apply the chain rule for linear equations. Then this question suddenly comes up and messes my whole grade up. I've searched and people use substitution method which is A level. Have you guys learnt this level of differentiation in your AS level too? or was it just me who didn't know?

 

[Kanekii]

HI guys, so I wrote my AS level pure math 1 paper today and it was easy but I couldn't get a 6 marks question right :'((
they gave: y= [(x^3+x^2)]^0.5
and in the question, the very first thing we had to do was differentiate it. Now I'm usually good at differentiation. I can do the product rule, quotient rule and chain rule even. However I had this assumption, god knows why that in AS level at least, we can only apply the chain rule for linear equations. Then this question suddenly comes up and messes my whole grade up. I've searched and people use substitution method which is A level. Have you guys learnt this level of differentiation in your AS level too? or was it just me who didn't know?

Sorry to hear that but you can differentiate it directly
Dy/dx=3x^3/[x^3+x^2]^0.5
We use quotient rule when we divide two different functions e.g x/x^2
We use product rule when we multiply two different functions e.g 3x.Cosx
We use chain rule when we three variables e.g x, y, t
Dy/Dx=Dy/Dt x Dt/dx.
Btw in differentiation we can differentiate linear or non linear equations.

 

[KashishV]

Sorry to hear that but you can differentiate it directly
Dy/dx=3x^3/[x^3+x^2]^0.5
We use quotient rule when we divide two different functions e.g x/x^2
We use product rule when we multiply two different functions e.g 3x.Cosx
We use chain rule when we three variables e.g x, y, t
Dy/Dx=Dy/Dt x Dt/dx.
Btw in differentiation we can differentiate linear or non linear equations.

Yes, I rechecked with my teacher too. The real fact was that you can only apply the chain rule to a linear equation while integrating. Stupid, stupid mistake.

 

[Thought blocker]

HI guys, so I wrote my AS level pure math 1 paper today and it was easy but I couldn't get a 6 marks question right :'((
they gave: y= [(x^3+x^2)]^0.5
and in the question, the very first thing we had to do was differentiate it. Now I'm usually good at differentiation. I can do the product rule, quotient rule and chain rule even. However I had this assumption, god knows why that in AS level at least, we can only apply the chain rule for linear equations. Then this question suddenly comes up and messes my whole grade up. I've searched and people use substitution method which is A level. Have you guys learnt this level of differentiation in your AS level too? or was it just me who didn't know?

This could be done with chain rule