OCR MEI M1 — Question 3 16 marks

Exam BoardOCR MEI
ModuleM1 (Mechanics 1)
Marks16
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicConstant acceleration (SUVAT)
TypeRead and interpret velocity-time graph
DifficultyModerate -0.3 This is a multi-part mechanics question requiring graph reading, basic differentiation (v = dy/dt, a = dv/dt), solving quadratic equations, and using SUVAT with integration. While it has many parts (7 marks typical), each individual step uses standard M1 techniques with no novel problem-solving required. Slightly easier than average due to straightforward calculus and routine application of kinematic principles.
Spec1.07i Differentiate x^n: for rational n and sums3.02b Kinematic graphs: displacement-time and velocity-time3.02c Interpret kinematic graphs: gradient and area3.02d Constant acceleration: SUVAT formulae3.02f Non-uniform acceleration: using differentiation and integration

3 A point P on a piece of machinery is moving in a vertical straight line. The displacement of P above ground level at time \(t\) seconds is \(y\) metres. The displacement-time graph for the motion during the time interval \(0 \leqslant t \leqslant 4\) is shown in Fig. 7. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{569e7c0e-7c33-47c9-b986-8587ea239f0a-3_1020_1333_352_439} \captionsetup{labelformat=empty} \caption{Fig. 7}
\end{figure}
  1. Using the graph, determine for the time interval \(0 \leqslant t \leqslant 4\) (A) the greatest displacement of P above its position when \(t = 0\),
    (B) the greatest distance of P from its position when \(t = 0\),
    (C) the time interval in which P is moving downwards,
    (D) the times when P is instantaneously at rest. The displacement of P in the time interval \(0 \leqslant t \leqslant 3\) is given by \(y = - 4 t ^ { 2 } + 8 t + 12\).
  2. Use calculus to find expressions in terms of \(t\) for the velocity and for the acceleration of P in the interval \(0 \leqslant t \leqslant 3\).
  3. At what times does P have a speed of \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in the interval \(0 \leqslant t \leqslant 3\) ? In the time interval \(3 \leqslant t \leqslant 4 , \mathrm { P }\) has a constant acceleration of \(32 \mathrm {~m} \mathrm {~s} ^ { - 2 }\). There is no sudden change in velocity when \(t = 3\).
  4. Find an expression in terms of \(t\) for the displacement of P in the interval \(3 \leqslant t \leqslant 4\).

Question 3:
Part (A)
AnswerMarks Guidance
False; this is a speed-time graph not one for displacement-timeM1, A1 Accept: "no information about direction of travel"; "distance is given by area under graph but this is not the same as displacement"; "speed is not a vector"; Do not accept: "the particle moves only in the positive direction"
Part (B)
AnswerMarks Guidance
TrueB1 Ignore subsequent working
Part (C)
AnswerMarks Guidance
TrueB1 Ignore subsequent working
Part (D)
AnswerMarks Guidance
False; the area under the graph is 420 not 400M1, A1 Accept area up to time 55 s is 400 m; the calculation in the false example must be correct
## Question 3:

### Part (A)
False; this is a speed-time graph not one for displacement-time | M1, A1 | Accept: "no information about direction of travel"; "distance is given by area under graph but this is not the same as displacement"; "speed is not a vector"; Do not accept: "the particle moves only in the positive direction"

### Part (B)
True | B1 | Ignore subsequent working

### Part (C)
True | B1 | Ignore subsequent working

### Part (D)
False; the area under the graph is 420 not 400 | M1, A1 | Accept area up to time 55 s is 400 m; the calculation in the false example must be correct

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3 A point P on a piece of machinery is moving in a vertical straight line. The displacement of P above ground level at time $t$ seconds is $y$ metres. The displacement-time graph for the motion during the time interval $0 \leqslant t \leqslant 4$ is shown in Fig. 7.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{569e7c0e-7c33-47c9-b986-8587ea239f0a-3_1020_1333_352_439}
\captionsetup{labelformat=empty}
\caption{Fig. 7}
\end{center}
\end{figure}
\begin{enumerate}[label=(\roman*)]
\item Using the graph, determine for the time interval $0 \leqslant t \leqslant 4$\\
(A) the greatest displacement of P above its position when $t = 0$,\\
(B) the greatest distance of P from its position when $t = 0$,\\
(C) the time interval in which P is moving downwards,\\
(D) the times when P is instantaneously at rest.

The displacement of P in the time interval $0 \leqslant t \leqslant 3$ is given by $y = - 4 t ^ { 2 } + 8 t + 12$.
\item Use calculus to find expressions in terms of $t$ for the velocity and for the acceleration of P in the interval $0 \leqslant t \leqslant 3$.
\item At what times does P have a speed of $4 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ in the interval $0 \leqslant t \leqslant 3$ ?

In the time interval $3 \leqslant t \leqslant 4 , \mathrm { P }$ has a constant acceleration of $32 \mathrm {~m} \mathrm {~s} ^ { - 2 }$. There is no sudden change in velocity when $t = 3$.
\item Find an expression in terms of $t$ for the displacement of P in the interval $3 \leqslant t \leqslant 4$.
\end{enumerate}

\hfill \mbox{\textit{OCR MEI M1  Q3 [16]}}