2006 Paper 3 Q11

Year: 2006
Paper: 3
Question Number: 11

Course: UFM Mechanics
Section: Momentum and Collisions 1

Difficulty: 1700.0 Banger: 1516.0

Problem

A lift of mass \(M\) and its counterweight of mass \(M\) are connected by a light inextensible cable which passes over a fixed frictionless pulley. The lift is constrained to move vertically between smooth guides. The distance between the floor and the ceiling of the lift is \(h\). Initially, the lift is at rest, and the distance between the top of the lift and the pulley is greater than \(h\). A small tile of mass \(m\) becomes detached from the ceiling of the lift and falls to the floor of the lift. Show that the speed of the tile just before the impact is \[ \sqrt{\frac{(2M-m)gh \;}{M}}\;. \] The coefficient of restitution between the tile and the floor of the lift is \(e\). Given that the magnitude of the impulsive force on the lift due to tension in the cable is equal to the magnitude of the impulsive force on the counterweight due to tension in the cable, show that the loss of energy of the system due to the impact is \(mgh(1-e^2)\). Comment on this result.

No solution available for this problem.

Rating Information

Difficulty Rating: 1700.0

Difficulty Comparisons: 0

Banger Rating: 1516.0

Banger Comparisons: 1

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Problem source
A lift of mass $M$ and 
its counterweight of mass $M$ are connected by a light 
inextensible cable which passes over a fixed frictionless pulley. The lift is
constrained to move vertically between smooth guides. The distance between
the floor and the ceiling of the lift is $h$. Initially, the lift is at
rest, and the distance between the top of the lift and the pulley is
greater than $h$. A small tile of mass $m$ becomes detached from the
ceiling of the lift and falls to the floor of the lift.
Show that the speed of the tile just before the impact
is
\[
\sqrt{\frac{(2M-m)gh \;}{M}}\;.
\]
The coefficient of restitution between the tile 
and the floor of the lift is $e$.
Given that  the magnitude of the impulsive 
force on the lift due to tension in the cable  
is equal to the magnitude of the impulsive force on the counterweight 
due to tension in the cable,
show that the loss of energy of the system due to the impact is $mgh(1-e^2)$.
Comment on this result.