Physics 2015: Rotational Motion
Purpose
Use the principle of conservation of energy to verify that gravitational
potential energy can be converted into rotational kinetic energy and
linear kinetic energy in a simple experiment.
Use the principle of conservation of momentum to explain transfer of
momentum during a collision of rotating bodies.
Use the principle of conservation of momentum to explain how
changing the shape of a rotating body affects the rotational velocity.
Physics 2015: Rotational Motion
Equivalent quantities in linear versus rotational motion
Linear Motion
Rotational Motion
Mass (m)
Distance (x)
Velocity (v)
Acceleration (a)
Moment of Inertia (I)
Angle (Ɵ)
Momentum (p = mv)
Angular Velocity (ω)
Angular Acceleration
(α)
Angular Momentum
(L = Iω)
Physics 2015: Rotational Motion
Type
Force
Position
Velocity
Momentum
Linear Motion
Rotational Motion
Physics 2015: Rotational Motion
Activity I: Rotating Bodies and Conservation of Energy
Setup: As hanging mass
drops, the plate starts to
rotate faster and faster.
Task: Design an experiment
to determine whether total
energy is conserved.
Important: Take into account
all types of energy you can
think of that are relevant here.
Diagram 2
Physics 2015: Rotational Motion

Note that the “Smart Pulley” (circled below) measures its own angular
velocity, which is NOT the same as that of the platter.

The “Smart Pulley’s” angular velocity and the platter’s angular velocity
are related. You need to find this relationship.
Physics 2015: Rotational Motion
Activity II: Collision Between Rotating Bodies
Setup: Main platter rotates,
auxiliary platter is dropped
on top of main platter
Task: Design an experiment
to determine whether total
angular momentum is conserved.
Important: You need to turn the
main platter upside down as shown
in the diagram.
Diagram 3
Physics 2015: Rotational Motion
Activity III: The Spinning “Ice Skater”
Setup: U-channel placed on top
of platter. Movable weights (little
carts with wheels) can be pulled
Inwards by a thread.
Task: Test conservation of angular
Momentum as carts are pulled in.
Hint: Threads must be routed through
holes on the side of the spindle and come
out on the top of the spindle, where you
can pull on them upwards.
Diagram 4
Physics 2015: Rotational Motion
Correction in Lab Manual
A few equations did not print out correctly in your manual on pages 80 and 81.
Please complete them as follows: