Classical Mechanics
Lecture 13: Collisions, Impulse and
Reference Frames
In-class Demonstrations
Demos © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 1
Demo: Basketball Drop with Small Ball on Top
Basketball Drop with Small Ball on Top
Description:
When a basketball is dropped
alone, it bounces a certain
height. When a smaller ball is
dropped alone, it bounces a
certain height. If the smaller
ball is placed on top of the
basketball, and they are
dropped simultaneously, the
small ball bounces significantly
higher than it would if
dropped alone.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 2
Demo: Basketball Drop with Small Ball on Top
Basketball Drop with Small Ball on Top
Description:
When a basketball is dropped
alone, it bounces a certain
height. When a smaller ball is
dropped alone, it bounces a
certain height. If the smaller
ball is placed on top of the
basketball, and they are
dropped simultaneously, the
small ball bounces significantly
higher than it would if
dropped alone.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 2
Demo: Collision of Bowling Ball and Golf Ball Pendula
Collision of Bowling Ball and Golf Ball Pendula
Description:
Students observe the collision of a
comparatively small mass (the golf ball) with a
large mass (the bowling ball) to see how linear
momentum is conserved.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 3
Demo: Bed Sheet with Raw Eggs
Bed Sheet with Raw Eggs
Description:
When we throw an egg
against a held sheet, the
momentum of the egg is
reversed by the force on
the egg by the sheet, but
the sheet 'softens the blow'
in that the force takes place
over a longer period of time
than if the egg were to be
thrown at a heavy and rigid
fixed object like the wall or
the floor. Because the
collision is longer in
duration, the maximum
force applied to the egg is
small enough that the egg
does not break.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 4
Demo: Rubber Pork Chop
Rubber Pork Chop
Description:
The painted white dot shows where the center of mass of the pork chop is. The pork
chop is thrown and students observe the parabolic behavior of its center of mass, no
matter how the chop is thrown.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 5
Demo: Ball Bearings Drop
Ball Bearings Drop
Description:
A metal tube is filled with 228 ball bearings, and then the tube is tipped such that they
are dropped from above a scale. When they hit the scale's platform, the average
weight registered on the scale is a measure of the pressure exerted on it by the falling
ball bearings. This is a large-scale model of what happens when pressure is caused by
individual molecules hitting the walls of a container.
Demonstrations © Dept. of Physics, Univ. of Illinois at Urbana-Champaign, 1996
Mechanics Lecture 13, Slide 6