Edexcel M1 — Question 7 12 marks

Exam BoardEdexcel
ModuleM1 (Mechanics 1)
Marks12
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicProjectiles
TypeModelling assumptions and limitations
DifficultyStandard +0.3 Parts (a) and (b) are standard SUVAT applications requiring direct formula substitution. Part (c) requires setting up equations for two objects and finding when they meet, which is a common M1 problem-solving task but involves more algebraic manipulation. Part (d) tests conceptual understanding. Overall slightly easier than average due to straightforward setup and standard techniques.
Spec3.02d Constant acceleration: SUVAT formulae3.02h Motion under gravity: vector form

Whilst looking over the edge of a vertical cliff, 122.5 metres in height, Jim dislodges a stone. The stone falls freely from rest towards the sea below. Ignoring the effect of air resistance,
  1. calculate the time it would take for the stone to reach the sea, [3 marks]
  2. find the speed with which the stone would hit the water. [2 marks]
Two seconds after the stone begins to fall, Jim throws a tennis ball downwards at the stone. The tennis ball's initial speed is \(u\) m s\(^{-1}\) and it hits the stone before they both reach the water.
  1. Find the minimum value of \(u\). [5 marks]
  2. If you had taken air resistance into account in your calculations, what effect would this have had on your answer to part (c)? Explain your answer. [2 marks]

Part (a):
AnswerMarks
\(s = 122.5\), \(u = 0\), \(a = g\) use \(s = ut + \frac{1}{4}at^2\)M1
\(122.5 = 4.9t^2 \Rightarrow t = 5\)M1 A1
Part (b):
AnswerMarks
\(v^2 = u^2 + 2as = 0 + 2g(122.5)\)M1
\(v = 49\) ms\(^{-1}\)A1
Part (c):
AnswerMarks
\(s = u(t - 2) + \frac{1}{4}(t - 2)^2\)M1
Jim must hit before \(t = 5\) i.e. \(122.5 = 3u + 4.9(3)^2\)M2 A1
\(3u = 78.4 \Rightarrow u = 26.1\) ms\(^{-1}\)A1
Part (d):
AnswerMarks Guidance
e.g. \(u\) larger as tennis ball would have experienced more air resistance due to greater speed / large surface area for massB2 (12)
**Part (a):**
$s = 122.5$, $u = 0$, $a = g$ use $s = ut + \frac{1}{4}at^2$ | M1 |
$122.5 = 4.9t^2 \Rightarrow t = 5$ | M1 A1 |

**Part (b):**
$v^2 = u^2 + 2as = 0 + 2g(122.5)$ | M1 |
$v = 49$ ms$^{-1}$ | A1 |

**Part (c):**
$s = u(t - 2) + \frac{1}{4}(t - 2)^2$ | M1 |
Jim must hit before $t = 5$ i.e. $122.5 = 3u + 4.9(3)^2$ | M2 A1 |
$3u = 78.4 \Rightarrow u = 26.1$ ms$^{-1}$ | A1 |

**Part (d):**
e.g. $u$ larger as tennis ball would have experienced more air resistance due to greater speed / large surface area for mass | B2 | (12)

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Whilst looking over the edge of a vertical cliff, 122.5 metres in height, Jim dislodges a stone. The stone falls freely from rest towards the sea below.

Ignoring the effect of air resistance,

\begin{enumerate}[label=(\alph*)]
\item calculate the time it would take for the stone to reach the sea, [3 marks]
\item find the speed with which the stone would hit the water. [2 marks]
\end{enumerate}

Two seconds after the stone begins to fall, Jim throws a tennis ball downwards at the stone. The tennis ball's initial speed is $u$ m s$^{-1}$ and it hits the stone before they both reach the water.

\begin{enumerate}[label=(\alph*)]
\setcounter{enumi}{2}
\item Find the minimum value of $u$. [5 marks]
\item If you had taken air resistance into account in your calculations, what effect would this have had on your answer to part (c)? Explain your answer. [2 marks]
\end{enumerate}

\hfill \mbox{\textit{Edexcel M1  Q7 [12]}}