Edexcel FM1 AS 2024 June — Question 1 9 marks

Exam BoardEdexcel
ModuleFM1 AS (Further Mechanics 1 AS)
Year2024
SessionJune
Marks9
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicMomentum and Collisions 1
TypeDirect collision with direction reversal
DifficultyStandard +0.3 This is a standard momentum and restitution problem with clearly defined masses, velocities, and collision conditions. It requires straightforward application of conservation of momentum and Newton's experimental law, with the direction reversal information making the setup clearer rather than harder. The three parts are routine calculations typical of FM1, making this slightly easier than an average A-level question overall.
Spec6.03b Conservation of momentum: 1D two particles6.03i Coefficient of restitution: e6.03j Perfectly elastic/inelastic: collisions6.03k Newton's experimental law: direct impact

  1. A particle \(A\) has mass \(2 m\) and a particle \(B\) has mass \(3 m\). The particles are moving in opposite directions along the same straight line and collide directly.
Immediately before the collision, the speed of \(A\) is \(2 u\) and the speed of \(B\) is \(u\). Immediately after the collision, the speed of \(A\) is \(0.5 u\) and the speed of \(B\) is \(w\). Given that the direction of motion of each particle is reversed by the collision,
  1. find \(w\) in terms of \(u\)
  2. find the coefficient of restitution between the particles,
  3. find, in terms of \(m\) and \(u\), the magnitude of the impulse received by \(A\) in the collision.

Question 1:
Part 1a:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of CLM: \(2m \times 2u - 3mu = -2m \times 0.5u + 3mw\)M1 Use of CLM, correct no. of terms, condone consistent extra \(g\)'s, sign errors, cancelled \(m\)'s, to produce an equation in \((m)\), \(u\) and \(w\) only. OR: Use of two impulse-momentum equations with \(I\) eliminated to produce equation in \((m)\), \(u\) and \(w\) only.
OR: \((I=)\ 2m(0.5u - -2u) = 3m(w - -u)\)A1 Correct equation in \((m)\), \(u\) and \(w\) only.
\(w = \dfrac{2u}{3}\), accept \(0.67u\) or betterA1 cao. Must see \(w = ku\)
(3 marks)
Part 1b:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of NELM1 Must be right way up with 'correct' terms but condone sign errors. Allow without the \(u\)'s
\(e = \dfrac{0.5u + \dfrac{2u}{3}}{2u + u}\)A1ft Correct unsimplified expression, ft on their \(w\)
\(\dfrac{7}{18}\), accept \(0.39\) or betterA1 cao
(3 marks)
Part 1c:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of impulse-momentum principle for \(A\) or \(B\)M1 Correct structure but condone sign errors (M0 if \(g\) included or \(m\)'s missing). Can score if \(m\) used for mass with a 'correct' pair of velocities.
\(\pm 2m(0.5u - -2u)\) OR \(\pm 3m\!\left(\dfrac{2u}{3} - -u\right)\)A1 Correct equation
\(5mu\)A1 cao
(3 marks)
Total: 9 marks
Question 2a:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of \(F = \frac{84000}{12}\)M1 Allow use of 84
Equation of motion horizontallyM1 Correct no. of terms, condone sign errors. Allow if they use 84 or 84000 as the driving force
\(\frac{84000}{12} - 490 \times 12 = 5000a\)A1 Correct equation
\(\frac{28}{125}\) or \(0.224\) or \(0.22\) (\(\text{m s}^{-2}\))A1 Accept 0.22
Question 2b:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of \(D = \frac{84000}{V}\)M1 Allow use of 84
Equation of motion parallel to road: \(D - 490V - 5000g\sin\alpha = 0\)M1 Equation in \(V\) only with correct no. of terms, condone sign errors and sin/cos confusion and omitted \(g\) with \(D\) in terms of \(V\)
\(\frac{84000}{V} - 490V - 5000g\sin\alpha = 0\)A1 Correct equation in \(V\) only
\(V = 10\) onlyA1 cao
Question 3a:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use the principle of conservation of mechanical energy and modelM1 Correct number of terms, dimensionally correct, condone sign errors. M0 if they use \(v^2 = u^2 + 2as\)
\(\frac{1}{2}mW^2 - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = mgh\)A1 Correct equation with at most one error
A1Correct equation
\(W = \sqrt{4gh} = 2\sqrt{gh}\)A1 Either (need \(W =\) )
Question 3b:
AnswerMarks Guidance
Answer/WorkingMark Guidance
\(R = mg\cos\theta\)M1 Condone sin/cos confusion and allow \(\cos\left(\frac{4}{5}\right)\) etc
\(F = \frac{1}{3}R\)M1 \(F = \frac{1}{3}R\)
\(F = \frac{4}{15}mg\)A1 Accept \(0.27\ mg\) or better
Question 3c:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use the work-energy principle and the modelM1 Correct number of terms, dimensionally correct, condone sign errors and sin/cos confusion and allow \(\cos\left(\frac{4}{5}\right)\) etc
\(A\) to \(B\): \(mgd\sin\theta - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = \frac{4}{15}mgd\)A1ft Correct equation with at most one error
or \(mg(h + d\sin\theta) - mgh - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = \frac{4}{15}mgd\)A1ft Correct equation ft on their answer to (b) (and (a) if they use \(A\) to the ground)
OR \(A\) to ground: \(mg(h + d\sin\theta) - \frac{1}{2}m\left(\sqrt{4gh}\right)^2 = \frac{4}{15}mgd\)
Solve for \(d\) in terms of \(h\) or \(h\) in terms of \(d\)M1 Solve for \(d\), must have at least 3 terms, with two of them in \(d\)
\(d = 3h\)A1 cao. N.B. No marks available if they don't use work-energy
Question 4a:
AnswerMarks Guidance
Answer/WorkingMark Guidance
Use of CLM OR NELM1 CLM: Correct no. of terms, condone consistent extra \(g\)'s, sign errors, cancelled \(m\)'s. OR NEL: \(e\) on the correct side but condone sign errors
\(mu = -m\frac{u}{5}(4e-1) + 4mv_Q\) OR \(v_Q + \frac{u}{5}(4e-1) = eu\)A1 Correct equation
\(v_Q = \frac{u}{5}(e+1)\)A1 Cao. Accept any equivalent two term expression
Question 4b:
AnswerMarks Guidance
Answer/WorkingMark Guidance
\(v_P = \pm\frac{fu}{5}(4e-1)\)B1 Seen or implied
\(= \pm\frac{2fu}{5}\)B1 Seen or implied
\(\text{KE Loss} = \frac{1}{2}m\left(\frac{2u}{5}\right)^2 - \frac{1}{2}m\left(\frac{2fu}{5}\right)^2\)M1 Allow negative of this and without \(e\) being substituted. Allow anything of the form \(\pm\left(\frac{1}{2}m(v_p)^2 - \frac{1}{2}m(fv_p)^2\right)\), provided that \(v_p\) has come from an attempt to put \(e = \frac{3}{4}\) in the given expression
\(= \frac{2mu^2}{25}(1-f^2)\)A1 Cao. Accept any equivalent two term expression, isw
Question 4c:
AnswerMarks Guidance
Answer/WorkingMark Guidance
\(v_Q = \frac{7u}{20}\)M1 For attempt to put \(e = \frac{3}{4}\) in their \(v_Q\) expression to give a multiple of \(u\), seen or implied at some stage
\(\frac{7u}{20} < \frac{2fu}{5}\)M1 Correct inequality for their speeds (which could involve \(e\)), provided it's dimensionally correct. Not available if \(Q\) is moving towards the wall
\(\frac{7}{8} < f\)A1 \(\frac{7}{8} < f\) oe
\(,\ 1\)B1 For \(f \leqslant 1\). N.B. All marks available if they go straight to \(\frac{7}{20} < \frac{2f}{5}\)
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# Question 1:

## Part 1a:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of CLM: $2m \times 2u - 3mu = -2m \times 0.5u + 3mw$ | M1 | Use of CLM, correct no. of terms, condone consistent extra $g$'s, sign errors, cancelled $m$'s, to produce an equation in $(m)$, $u$ and $w$ only. **OR:** Use of two impulse-momentum equations with $I$ eliminated to produce equation in $(m)$, $u$ and $w$ only. |
| **OR:** $(I=)\ 2m(0.5u - -2u) = 3m(w - -u)$ | A1 | Correct equation in $(m)$, $u$ and $w$ only. |
| $w = \dfrac{2u}{3}$, accept $0.67u$ or better | A1 | cao. Must see $w = ku$ |
| **(3 marks)** | | |

## Part 1b:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of NEL | M1 | Must be right way up with 'correct' terms but condone sign errors. Allow without the $u$'s |
| $e = \dfrac{0.5u + \dfrac{2u}{3}}{2u + u}$ | A1ft | Correct unsimplified expression, ft on their $w$ |
| $\dfrac{7}{18}$, accept $0.39$ or better | A1 | cao |
| **(3 marks)** | | |

## Part 1c:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of impulse-momentum principle for $A$ or $B$ | M1 | Correct structure but condone sign errors (M0 if $g$ included or $m$'s missing). Can score if $m$ used for mass with a 'correct' pair of velocities. |
| $\pm 2m(0.5u - -2u)$ **OR** $\pm 3m\!\left(\dfrac{2u}{3} - -u\right)$ | A1 | Correct equation |
| $5mu$ | A1 | cao |
| **(3 marks)** | | |

**Total: 9 marks**

## Question 2a:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of $F = \frac{84000}{12}$ | M1 | Allow use of 84 |
| Equation of motion horizontally | M1 | Correct no. of terms, condone sign errors. Allow if they use 84 or 84000 as the driving force |
| $\frac{84000}{12} - 490 \times 12 = 5000a$ | A1 | Correct equation |
| $\frac{28}{125}$ or $0.224$ or $0.22$ ($\text{m s}^{-2}$) | A1 | Accept 0.22 |

## Question 2b:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of $D = \frac{84000}{V}$ | M1 | Allow use of 84 |
| Equation of motion parallel to road: $D - 490V - 5000g\sin\alpha = 0$ | M1 | Equation in $V$ only with correct no. of terms, condone sign errors and sin/cos confusion and omitted $g$ with $D$ in terms of $V$ |
| $\frac{84000}{V} - 490V - 5000g\sin\alpha = 0$ | A1 | Correct equation in $V$ only |
| $V = 10$ only | A1 | cao |

## Question 3a:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use the principle of conservation of mechanical energy and model | M1 | Correct number of terms, dimensionally correct, condone sign errors. M0 if they use $v^2 = u^2 + 2as$ |
| $\frac{1}{2}mW^2 - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = mgh$ | A1 | Correct equation with at most one error |
| | A1 | Correct equation |
| $W = \sqrt{4gh} = 2\sqrt{gh}$ | A1 | Either (need $W =$ ) |

## Question 3b:

| Answer/Working | Mark | Guidance |
|---|---|---|
| $R = mg\cos\theta$ | M1 | Condone sin/cos confusion and allow $\cos\left(\frac{4}{5}\right)$ etc |
| $F = \frac{1}{3}R$ | M1 | $F = \frac{1}{3}R$ |
| $F = \frac{4}{15}mg$ | A1 | Accept $0.27\ mg$ or better |

## Question 3c:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use the work-energy principle and the model | M1 | Correct number of terms, dimensionally correct, condone sign errors and sin/cos confusion and allow $\cos\left(\frac{4}{5}\right)$ etc |
| $A$ to $B$: $mgd\sin\theta - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = \frac{4}{15}mgd$ | A1ft | Correct equation with at most one error |
| or $mg(h + d\sin\theta) - mgh - \frac{1}{2}m\left(\sqrt{2gh}\right)^2 = \frac{4}{15}mgd$ | A1ft | Correct equation ft on their answer to (b) (and (a) if they use $A$ to the ground) |
| **OR** $A$ to ground: $mg(h + d\sin\theta) - \frac{1}{2}m\left(\sqrt{4gh}\right)^2 = \frac{4}{15}mgd$ | | |
| Solve for $d$ in terms of $h$ or $h$ in terms of $d$ | M1 | Solve for $d$, must have at least 3 terms, with two of them in $d$ |
| $d = 3h$ | A1 | cao. N.B. No marks available if they don't use work-energy |

## Question 4a:

| Answer/Working | Mark | Guidance |
|---|---|---|
| Use of CLM **OR** NEL | M1 | CLM: Correct no. of terms, condone consistent extra $g$'s, sign errors, cancelled $m$'s. **OR** NEL: $e$ on the correct side but condone sign errors |
| $mu = -m\frac{u}{5}(4e-1) + 4mv_Q$ **OR** $v_Q + \frac{u}{5}(4e-1) = eu$ | A1 | Correct equation |
| $v_Q = \frac{u}{5}(e+1)$ | A1 | Cao. Accept any equivalent two term expression |

## Question 4b:

| Answer/Working | Mark | Guidance |
|---|---|---|
| $v_P = \pm\frac{fu}{5}(4e-1)$ | B1 | Seen or implied |
| $= \pm\frac{2fu}{5}$ | B1 | Seen or implied |
| $\text{KE Loss} = \frac{1}{2}m\left(\frac{2u}{5}\right)^2 - \frac{1}{2}m\left(\frac{2fu}{5}\right)^2$ | M1 | Allow negative of this and without $e$ being substituted. Allow anything of the form $\pm\left(\frac{1}{2}m(v_p)^2 - \frac{1}{2}m(fv_p)^2\right)$, provided that $v_p$ has come from an attempt to put $e = \frac{3}{4}$ in the given expression |
| $= \frac{2mu^2}{25}(1-f^2)$ | A1 | Cao. Accept any equivalent two term expression, isw |

## Question 4c:

| Answer/Working | Mark | Guidance |
|---|---|---|
| $v_Q = \frac{7u}{20}$ | M1 | For attempt to put $e = \frac{3}{4}$ in their $v_Q$ expression to give a multiple of $u$, seen or implied at some stage |
| $\frac{7u}{20} < \frac{2fu}{5}$ | M1 | Correct inequality for their speeds (which could involve $e$), provided it's dimensionally correct. Not available if $Q$ is moving towards the wall |
| $\frac{7}{8} < f$ | A1 | $\frac{7}{8} < f$ oe |
| $,\ 1$ | B1 | For $f \leqslant 1$. N.B. All marks available if they go straight to $\frac{7}{20} < \frac{2f}{5}$ |

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\begin{enumerate}
  \item A particle $A$ has mass $2 m$ and a particle $B$ has mass $3 m$. The particles are moving in opposite directions along the same straight line and collide directly.
\end{enumerate}

Immediately before the collision, the speed of $A$ is $2 u$ and the speed of $B$ is $u$. Immediately after the collision, the speed of $A$ is $0.5 u$ and the speed of $B$ is $w$.

Given that the direction of motion of each particle is reversed by the collision,\\
(a) find $w$ in terms of $u$\\
(b) find the coefficient of restitution between the particles,\\
(c) find, in terms of $m$ and $u$, the magnitude of the impulse received by $A$ in the collision.

\hfill \mbox{\textit{Edexcel FM1 AS 2024 Q1 [9]}}