Year: 2005
Paper: 2
Question Number: 11
Course: LFM Pure and Mechanics
Section: Pulley systems
No solution available for this problem.
Difficulty Rating: 1600.0
Difficulty Comparisons: 0
Banger Rating: 1502.0
Banger Comparisons: 2
A plane is inclined at an
angle $\arctan \frac34$ to the horizontal and
a small, smooth, light pulley~$P$
is fixed to the top of the plane. A string, $APB$, passes over the pulley.
A particle of mass~$m_1$
is attached to the string at $A$ and rests on the inclined plane with $AP$
parallel to a line of greatest slope in the plane.
A particle of mass $m_2$, where $m_2>m_1$,
is attached to the string at $B$
and hangs freely with $BP$
vertical. The coefficient of
friction between the particle at $A$
and the plane is $ \frac{1}{2}$.
The system is released from rest with the string taut.
Show that the acceleration of the
particles is $\ds \frac{m_2-m_1}{m_2+m_1}g$.
At a time $T$ after release, the string breaks.
Given that the particle at $A$
does not reach the pulley at any point in its motion,
find an expression in terms of $T$ for the time
after release at which the particle at $A$
reaches its maximum height. It is found that, regardless
of when the string broke, this time is equal to the time
taken by the particle at $A$ to descend
from its point of maximum height to the point
at which it was released. Find the ratio $m_1 : m_2$.
\noindent
[Note that $\arctan \frac34$ is another notation for $\tan^{-1} \frac34\,$.]