Year: 2006
Paper: 3
Question Number: 11
Course: UFM Mechanics
Section: Momentum and Collisions 1
No solution available for this problem.
Difficulty Rating: 1700.0
Difficulty Comparisons: 0
Banger Rating: 1516.0
Banger Comparisons: 1
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.