CAIE FP2 2014 June — Question 2

Exam BoardCAIE
ModuleFP2 (Further Pure Mathematics 2)
Year2014
SessionJune
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicProjectiles
TypeBasic trajectory calculations
DifficultyStandard +0.0 Unable to rate — garbled OCR content
Spec3.02a Kinematics language: position, displacement, velocity, acceleration3.03c Newton's second law: F=ma one dimension

2 A particle \(P\) of mass \(m \mathrm {~kg}\) moves on an arc of a circle with centre \(O\) and radius \(a\) metres. At time \(t = 0\) the particle is at the point \(A\). At time \(t\) seconds, angle \(P O A = \sin ^ { 2 } 2 t\). Show that the radial component of the acceleration of \(P\) at time \(t\) seconds has magnitude \(\left( 4 a \sin ^ { 2 } 4 t \right) \mathrm { m } \mathrm { s } ^ { - 2 }\). Find
  1. the value of \(t\) when the transverse component of the acceleration of \(P\) is first equal to zero,
  2. the magnitude of the resultant force acting on \(P\) when \(t = \frac { 1 } { 12 } \pi\).

Question 2:
AnswerMarks Guidance
Answer/WorkingMarks Guidance
\(r(\frac{d\theta}{dt})^2 = (2\sin 2t)(2\cos 2t) = 2\sin 4t\)M1 Find radial acceleration from \(r(\frac{d\theta}{dt})^2 \equiv r\omega^2\)
\(r(\frac{d\theta}{dt})^2 = 4a\sin^2 4t\) A.G.A1
Part (i)
AnswerMarks Guidance
Answer/WorkingMarks Guidance
\(\frac{d^2\theta}{dt^2} = 8\cos 4t = 0\)M1 Find \(t\) by equating \(\frac{d^2\theta}{dt^2}\) to 0
\(t = \frac{\pi}{8}\) or \(0.393\)A1
Part (ii)
AnswerMarks Guidance
Answer/WorkingMarks Guidance
\(4ma\sin^2\frac{4\pi}{12} = 3ma\) and \(8ma\cos\frac{4\pi}{12} = 4ma\)M1 Find radial and transverse components of force
\(\sqrt{3^2 + 4^2}\, ma = 5ma\)A1 Combine to find magnitude of resultant force
# Question 2:

| Answer/Working | Marks | Guidance |
|---|---|---|
| $r(\frac{d\theta}{dt})^2 = (2\sin 2t)(2\cos 2t) = 2\sin 4t$ | M1 | Find radial acceleration from $r(\frac{d\theta}{dt})^2 \equiv r\omega^2$ |
| $r(\frac{d\theta}{dt})^2 = 4a\sin^2 4t$ **A.G.** | A1 | |

## Part (i)
| Answer/Working | Marks | Guidance |
|---|---|---|
| $\frac{d^2\theta}{dt^2} = 8\cos 4t = 0$ | M1 | Find $t$ by equating $\frac{d^2\theta}{dt^2}$ to 0 |
| $t = \frac{\pi}{8}$ or $0.393$ | A1 | |

## Part (ii)
| Answer/Working | Marks | Guidance |
|---|---|---|
| $4ma\sin^2\frac{4\pi}{12} = 3ma$ and $8ma\cos\frac{4\pi}{12} = 4ma$ | M1 | Find radial and transverse components of force |
| $\sqrt{3^2 + 4^2}\, ma = 5ma$ | A1 | Combine to find magnitude of resultant force |

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2 A particle $P$ of mass $m \mathrm {~kg}$ moves on an arc of a circle with centre $O$ and radius $a$ metres. At time $t = 0$ the particle is at the point $A$. At time $t$ seconds, angle $P O A = \sin ^ { 2 } 2 t$. Show that the radial component of the acceleration of $P$ at time $t$ seconds has magnitude $\left( 4 a \sin ^ { 2 } 4 t \right) \mathrm { m } \mathrm { s } ^ { - 2 }$.

Find\\
(i) the value of $t$ when the transverse component of the acceleration of $P$ is first equal to zero,\\
(ii) the magnitude of the resultant force acting on $P$ when $t = \frac { 1 } { 12 } \pi$.

\hfill \mbox{\textit{CAIE FP2 2014 Q2}}