CAIE FP1 2019 November — Question 1 6 marks

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2019
SessionNovember
Marks6
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicCentre of Mass 2
TypeCentre of mass of lamina by integration
DifficultyStandard +0.8 This is a standard centroid calculation requiring integration of x^a and x·x^a, then applying centroid formulas. While it involves algebraic manipulation with a parameter and requires careful bookkeeping of the formulas, it's a direct application of standard techniques with no conceptual surprises. The 6 marks reflect moderate computational work rather than exceptional difficulty.
Spec4.08e Mean value of function: using integral

The curve \(C\) has equation \(y = x^a\) for \(0 \leq x \leq 1\), where \(a\) is a positive constant. Find, in terms of \(a\), the coordinates of the centroid of the region enclosed by \(C\), the line \(x = 1\) and the \(x\)-axis. [6]

Question 1:
AnswerMarks
1xa+1 1
1 1
A=∫ xadx= =
 
a+1 a+1
0  
AnswerMarks Guidance
0B1 Finds area of region.
1 1  xa+2  1 1
Ax =∫xydx =∫xa+1 dx=   =
a+2 a+2
 
AnswerMarks Guidance
0 0 0M1 A1 1
Finds ∫xydx .
0
1 1  x2a+1  1 1
2Ay =∫y2 dx =∫x2a dx=   =
2a+1 2a+1
 
AnswerMarks Guidance
0 0 0M1 A1 1
Finds ∫y2dx .
0
( )=  a +1 a + 1 
x,y   a + 2 , 2 ( 2a + 1 )  
AnswerMarks Guidance
 A1 Both coordinates correct.
6
AnswerMarks Guidance
QuestionAnswer Marks
Question 1:
1 | xa+1 1
1 1
A=∫ xadx= =
 
a+1 a+1
0  
0 | B1 | Finds area of region.
1 1  xa+2  1 1
Ax =∫xydx =∫xa+1 dx=   =
a+2 a+2
 
0 0 0 | M1 A1 | 1
Finds ∫xydx .
0
1 1  x2a+1  1 1
2Ay =∫y2 dx =∫x2a dx=   =
2a+1 2a+1
 
0 0 0 | M1 A1 | 1
Finds ∫y2dx .
0
( )=  a +1 a + 1 
x,y   a + 2 , 2 ( 2a + 1 )  
  | A1 | Both coordinates correct.
6
Question | Answer | Marks | Guidance
The curve $C$ has equation $y = x^a$ for $0 \leq x \leq 1$, where $a$ is a positive constant. Find, in terms of $a$, the coordinates of the centroid of the region enclosed by $C$, the line $x = 1$ and the $x$-axis. [6]

\hfill \mbox{\textit{CAIE FP1 2019 Q1 [6]}}