CAIE
FP2
2012
November
Q8
8 The yield of a particular crop on a farm is thought to depend principally on the amount of sunshine during the growing season. For a random sample of 8 years, the average yield, \(y\) kilograms per square metre, and the average amount of sunshine per day, \(x\) hours, are recorded. The results are given in the following table.
| \(x\) | 12.2 | 10.4 | 5.2 | 6.3 | 11.8 | 10.0 | 14.2 | 2.3 |
| \(y\) | 15 | 9 | 10 | 7 | 8 | 11 | 12 | 6 |
$$\left[ \Sigma x = 72.4 , \Sigma x ^ { 2 } = 769.9 , \Sigma y = 78 , \Sigma y ^ { 2 } = 820 , \Sigma x y = 761.3 . \right]$$
- Find the equation of the regression line of \(y\) on \(x\).
- Find the product moment correlation coefficient.
- Test, at the \(5 \%\) significance level, whether there is positive correlation between the average yield and the average amount of sunshine per day.
CAIE
FP2
2012
November
Q9
9 marks
9 The leaves from oak trees growing in two different areas \(A\) and \(B\) are being measured. The lengths, in cm , of a random sample of 7 oak leaves from area \(A\) are
$$6.2 , \quad 8.3 , \quad 7.8 , \quad 9.3 , \quad 10.2 , \quad 8.4 , \quad 7.2$$
Assuming that the distribution is normal, find a 95\% confidence interval for the mean length of oak leaves from area \(A\).
The lengths, in cm, of a random sample of 5 oak leaves from area \(B\) are
$$5.9 , \quad 7.4 , \quad 6.8 , \quad 8.2 , \quad 8.7$$
Making suitable assumptions, which should be stated, test, at the \(5 \%\) significance level, whether the mean length of oak leaves from area \(A\) is greater than the mean length of oak leaves from area \(B\). [9]
CAIE
FP2
2012
November
Q10 OR
A continuous random variable \(X\) is believed to have the probability density function f given by
$$f ( x ) = \begin{cases} \frac { 3 } { 10 } \left( 5 x - x ^ { 2 } - 4 \right) & 2 \leqslant x < 4
0 & \text { otherwise } \end{cases}$$
A random sample of 60 observations was taken and these values are summarised in the following grouped frequency table.
| Interval | \(2 \leqslant x < 2.4\) | \(2.4 \leqslant x < 2.8\) | \(2.8 \leqslant x < 3.2\) | \(3.2 \leqslant x < 3.6\) | \(3.6 \leqslant x < 4\) |
| Observed frequency | 19 | 17 | 16 | 8 | 0 |
The estimated mean, based on the grouped data in the table above, is 2.69 , correct to 2 decimal places. It is decided that a goodness of fit test will only be conducted if the mean predicted from the probability density function is within \(10 \%\) of the estimated mean. Show that this condition is satisfied.
The relevant expected frequencies are as follows.
| Interval | \(2 \leqslant x < 2.4\) | \(2.4 \leqslant x < 2.8\) | \(2.8 \leqslant x < 3.2\) | \(3.2 \leqslant x < 3.6\) | \(3.6 \leqslant x < 4\) |
| Expected frequency | 15.456 | 16.032 | 14.304 | 10.272 | 3.936 |
Show how the expected frequency for the interval \(3.2 \leqslant x < 3.6\) is obtained.
Carry out the goodness of fit test at the 10\% significance level.
CAIE
FP2
2012
November
Q1
1
\includegraphics[max width=\textwidth, alt={}, center]{d3e9a568-a9ea-483e-8e65-90fdc4a69781-2_216_1205_253_470}
A rigid body consists of two uniform circular discs, each of mass \(m\) and radius \(a\), the centres of which are rigidly attached to the ends \(A\) and \(B\) of a uniform rod of mass \(3 m\) and length \(10 a\). The discs and the rod are in the same plane and \(O\) is the point on the rod such that \(A O = 4 a\) (see diagram). Show that the moment of inertia of the body about an axis through \(O\) perpendicular to the plane of the discs is \(81 m a ^ { 2 }\).
CAIE
FP2
2012
November
Q2
2 A small bead of mass \(m\) is threaded on a thin smooth wire which forms a circle of radius \(a\). The wire is fixed in a vertical plane. A light inextensible string is attached to the bead and passes through a small smooth ring fixed at the centre of the circle. The other end of the string is attached to a particle of mass \(4 m\) which hangs freely under gravity. The bead is projected from the lowest point of the wire with speed \(\sqrt { } ( k g a )\). Show that, when the angle between the two parts of the string is \(\theta\), the normal force exerted on the bead by the wire is \(m g ( 3 \cos \theta + k - 6 )\), towards the centre.
Given that the bead reaches the highest point of the wire, find an inequality which must be satisfied by \(k\).
CAIE
FP2
2012
November
Q5
5 Four identical uniform rods, each of mass \(m\) and length \(2 a\), are rigidly joined to form a square frame \(A B C D\). Show that the moment of inertia of the frame about an axis through \(A\) perpendicular to the plane of the frame is \(\frac { 40 } { 3 } m a ^ { 2 }\).
The frame is suspended from \(A\) and is able to rotate freely under gravity in a vertical plane, about a horizontal axis through \(A\). When the frame is at rest with \(C\) vertically below \(A\), it is given an angular velocity \(\sqrt { } \left( \frac { 6 g } { 5 a } \right)\). Find the angular velocity of the frame when \(A C\) makes an angle \(\theta\) with the downward vertical through \(A\).
When \(A C\) is horizontal, the speed of \(C\) is \(k \sqrt { } ( g a )\). Find the value of \(k\) correct to 3 significant figures.
CAIE
FP2
2012
November
Q9
9 Experiments are conducted to test the breaking strength of each of two types of rope, \(P\) and \(Q\). A random sample of 50 ropes of type \(P\) and a random sample of 70 ropes of type \(Q\) are selected. The breaking strengths, \(p\) and \(q\), measured in appropriate units, are summarised as follows.
$$\Sigma p = 321.2 \quad \Sigma p ^ { 2 } = 2120.0 \quad \Sigma q = 475.3 \quad \Sigma q ^ { 2 } = 3310.0$$
Test, at the \(10 \%\) significance level, whether the mean breaking strengths of type \(P\) and type \(Q\) ropes are the same.
CAIE
FP2
2012
November
Q10
10 Delegates who travelled to a conference were asked to report the distance, \(y \mathrm {~km}\), that they had travelled and the time taken, \(x\) minutes. The values reported by a random sample of 8 delegates are given in the following table.
| Delegate | \(A\) | \(B\) | \(C\) | \(D\) | \(E\) | \(F\) | \(G\) | \(H\) |
| \(x\) | 90 | 46 | 72 | 98 | 52 | 65 | 105 | 82 |
| \(y\) | 90 | 55 | 69 | 85 | 45 | 50 | 110 | 74 |
$$\left[ \Sigma x = 610 , \Sigma x ^ { 2 } = 49682 , \Sigma y = 578 , \Sigma y ^ { 2 } = 45212 , \Sigma x y = 47136 . \right]$$
Find the equations of the regression lines of \(y\) on \(x\) and of \(x\) on \(y\).
Estimate the time taken by a delegate who travelled 100 km to the conference.
Calculate the product moment correlation coefficient for this sample.
CAIE
FP2
2013
November
Q1
1
\includegraphics[max width=\textwidth, alt={}, center]{b486decd-75b8-44bd-889f-2472f1163871-2_553_435_258_854}
Three identical uniform rods, \(A B , B C\) and \(C D\), each of mass \(M\) and length \(2 a\), are rigidly joined to form three sides of a square. A uniform circular disc, of mass \(\frac { 2 } { 3 } M\) and radius \(a\), has the opposite ends of one of its diameters attached to \(A\) and \(D\) respectively. The disc and the rods all lie in the same plane (see diagram). Find the moment of inertia of the system about the axis \(A D\).
CAIE
FP2
2013
November
Q2
2 The point \(O\) is on the fixed line \(l\). The point \(A\) on \(l\) is such that \(O A = 3 \mathrm {~m}\). A particle \(P\) oscillates on \(l\) in simple harmonic motion with centre \(O\) and period \(\pi\) seconds. When \(P\) is at \(A\) its speed is \(12 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). Find the speed of \(P\) when it is at the point \(B\) on \(l\), where \(O B = 6 \mathrm {~m}\) and \(B\) is on the same side of \(O\) as \(A\).
Find, correct to 2 decimal places, the time, in seconds, taken for \(P\) to travel directly from \(A\) to \(B\).
CAIE
FP2
2013
November
Q3
9 marks
3
\includegraphics[max width=\textwidth, alt={}, center]{b486decd-75b8-44bd-889f-2472f1163871-2_570_419_1539_863}
A uniform disc, of mass 2 kg and radius 0.2 m , is free to rotate in a vertical plane about a smooth horizontal axis through its centre. One end of a light inextensible string is attached to a point on the rim of the disc and the string is wound round the rim. The other end of the string is attached to a small block of mass 4 kg , which hangs freely (see diagram). The system is released from rest. During the subsequent motion, the block experiences a constant resistance to its motion, of magnitude \(R \mathrm {~N}\). Given that the angular speed of the disc after it has turned through 2 radians is \(5 \mathrm { rad } \mathrm { s } ^ { - 1 }\), find \(R\) and the tension in the string.
[0pt]
[9]
CAIE
FP2
2013
November
Q5
5 Two uniform small smooth spheres \(A\) and \(B\), of equal radii, have masses \(2 m\) and \(m\) respectively. They lie at rest on a smooth horizontal plane. Sphere \(A\) is projected directly towards \(B\) with speed \(u\). After the collision \(B\) goes on to collide directly with a fixed smooth vertical barrier, before colliding with \(A\) again. The coefficient of restitution between \(A\) and \(B\) is \(\frac { 2 } { 3 }\) and the coefficient of restitution between \(B\) and the barrier is \(e\). After the second collision between \(A\) and \(B\), the speed of \(B\) is five times the speed of \(A\). Find the two possible values of \(e\).