Challenging +1.2 This is a standard Further Maths mechanics problem requiring application of coefficient of restitution, conservation of momentum parallel to the barrier, and energy loss. While it involves multiple equations and algebraic manipulation across three conditions, the approach is methodical and follows well-established techniques for oblique collisions. The given information (tan θ and energy loss percentage) makes the problem more structured than open-ended, placing it moderately above average difficulty.
\includegraphics{figure_2}
A particle \(P\) of mass \(m\) is moving with speed \(u\) on a fixed smooth horizontal surface. It collides at an angle \(\alpha\) with a fixed smooth vertical barrier. After the collision, \(P\) moves at an angle \(\theta\) with the barrier, where \(\tan\theta = \frac{1}{3}\) (see diagram). The coefficient of restitution between \(P\) and the barrier is \(e\). The particle \(P\) loses 20% of its kinetic energy as a result of the collision.
Find the value of \(e\). [5]
KE reduced by 20%, so 1mu2 cos2e2sin2 41mu2
Answer
Marks
Guidance
2 5 2
M1
Dimensionally correct equation in u or v, but not
both. Must have either or , but not both.
Must see 4 on the correct side of the equation.
5
4
Eliminate e: cos
Answer
Marks
5
A1
2
e
Answer
Marks
Guidance
3
A1
Question
Answer
Marks
2
Alternative method for question 2
Parallel to wall vcosucos
Answer
Marks
Guidance
Perpendicular to wall vsineusin
M1
Both
5 2 5 5v 2 5v
sin , cos usin , ucos
5 5 5e 5
Answer
Marks
A1
4v2 v2
u2 u2cos2u2sin2
Answer
Marks
Guidance
5 5e2
A1
v2 1
AEF, e.g. 4
5 e2
1 4 1 2 v2 1
mv2 mu2 m 4
Answer
Marks
Guidance
2 5 2 5 5 e2
M1
Dimensionally correct equation in v.
Must have either or , but not both.
4 2
Must see or on the correct side of the
5 5
equation.
2
e
Answer
Marks
3
A1
5
Answer
Marks
Guidance
Question
Answer
Marks
Question 2:
2 | Parallel to wall vcosucos
Perpendicular to wall vsineusin | M1 | Both
1
Dividing, e
2tan | A1 | AEF
KE reduced by 20%, so 1mu2 cos2e2sin2 41mu2
2 5 2 | M1 | Dimensionally correct equation in u or v, but not
both. Must have either or , but not both.
Must see 4 on the correct side of the equation.
5
4
Eliminate e: cos
5 | A1
2
e
3 | A1
Question | Answer | Marks | Guidance
2 | Alternative method for question 2
Parallel to wall vcosucos
Perpendicular to wall vsineusin | M1 | Both
5 2 5 5v 2 5v
sin , cos usin , ucos
5 5 5e 5
| A1
4v2 v2
u2 u2cos2u2sin2
5 5e2 | A1 | v2 1
AEF, e.g. 4
5 e2
1 4 1 2 v2 1
mv2 mu2 m 4
2 5 2 5 5 e2 | M1 | Dimensionally correct equation in v.
Must have either or , but not both.
4 2
Must see or on the correct side of the
5 5
equation.
2
e
3 | A1
5
Question | Answer | Marks | Guidance
\includegraphics{figure_2}
A particle $P$ of mass $m$ is moving with speed $u$ on a fixed smooth horizontal surface. It collides at an angle $\alpha$ with a fixed smooth vertical barrier. After the collision, $P$ moves at an angle $\theta$ with the barrier, where $\tan\theta = \frac{1}{3}$ (see diagram). The coefficient of restitution between $P$ and the barrier is $e$. The particle $P$ loses 20% of its kinetic energy as a result of the collision.
Find the value of $e$. [5]
\hfill \mbox{\textit{CAIE Further Paper 3 2023 Q2 [5]}}