MAXWELL S PENDULUM Description and Specifications for Lab Tenders
MAXWELL S PENDULUM.
MAXWELL S PENDULUM The mechanical energy of a system is the result of the sum of
kinetic and potential energies.
When there are only conservative forces, the principle stating
that “during transformation, partial energies are transformed,
whereas mechanical energy is preserved” is valid.
Maxwell’s pendulum is a very good example of the principle of
conservation of mechanical energy. The system consists of a
flywheel. Two wires are wound around the flywheel axis in the
same direction, whereas the opposite ends are connected with
a horizontal support. Winding the wires around the axis will
load the flywheel so that it will reach a certain height from the
reference plane. When released, the flywheel starts to go down
gathering speed. When arrived at the lowest point allowed
by unwinding wires, pendulum will rewind in the opposite
direction and starts going upwards again. In ideal conditions it
would come back to the same starting height ; however motion
is damped by frictions with wires and with the medium (air) and
after a certain number of oscillations, pendulum will stop in the
lowest point allowed by wires.
The principle of conservation of energy is used to determine
pendulum’s period, that is the time spent by the flywheel in
going down and up : the variations of kinetic energy of both
translation and rotation will compensate the variations of
potential energy. All the energy is potential at the maximum
height, whereas all the energy available at the lowest point is
kinetic. That could continue ad infinitum, in an ideal system,
but actually the wheel will stop at a certain point because of
friction.
Pendulum consists of a thin metallic disk with a hole in its
centre where a shaft, fixed to the disk with a screw, is inserted.
The shaft is a metallic bar turned and drilled to realize Maxwell’s
pendulum with different values of R/r ratio. The two wires
supporting the pendulum are run through two thin crosswise
holes drilled at the ends of each section.
The system must also be equipped with two sensors (a force
sensor and distance sensor) that are interfaced to datalogger
and to PC for the study of system kinematics and dynamics.
Pendulum hooks on to the force sensor via a pair of parallel
wires tied to pendulum ends on the main axis. Values of R/r
depend on the pair of holes being used.
The position sensor is arranged at the base of the system and
it enables to assess the speed with which the wheel arrives at
the end of its travel, using sonar technique.
The system used in this equipment is characterized by a
high frequency of data acquisition and by a versatile dataprocessing
software enabling to study not only the up and
down movement of pendulum, but also the phase of collision
with the wire end, besides checking the equality between
impulse of the force applied by the wire to the pendulum and
the variation of pendulum momentum, in an experimental way.
TRAINING PROGRAM
• conservation and dissipation of mechanical energy
• translation energy versus time
• rotation energy versus time
• potential energy versus time
• variation of momentum
• moment of inertia
• angular velocity
• angular acceleration
• instantaneous speed
• weight of pendulum in static and dynamic conditions
• impulse-momentum theorem
• calculating the period of pendulum
COMPONENTS
• 1 supporting base
• 2 vertical rods for mounting the wheel
• 2 horizontal rods for supporting the wheel and the force
sensor
• 1 wheel with pin of different radii
• string
• 4 terminals