Equivalent descent time

Right triangle shown above is made of taut string.
Each side contains a brass ball that is free to slide along the string segment.
Time of descent, from top to bottom of segment, is equivalent for each of the three balls.
This is true for any right triangle, with vertical hypotenuse, as the side lengths are reduced by the same factor as the rate of acceleration.
String is mounted on white-board material so instructor can derive equations alongside triangle using a dry erase marker.
Located in L02, section B3

g ball

Ball can be used to measure the free-fall time of an object.
Release of a button on ball’s face starts a digital timer. Timer automatically stops upon collision.
Please use a landing cushion, such as the styrofoam pad shown above, to prevent the risk of cracking face of digital timer.

Hold both ends of the chain- one end in each hand- so that the chain hangs freely and forms a U shape.
When one end of the chain is released it accelerates toward the ground faster than g. To prove it, drop an object simultaneously with the chain end, and listen to hear which one strikes the ground first.
Requires standing on ladder.
Chain located in L02, section B3. Plastic balls in section A2.

Nuts are tied to two separate ropes. Spacing between nuts on rope 1 is constant; spacing between nuts on rope 2 goes as the square of the distance from the end of the rope.
Hang ropes vertically and drop onto wooden platform. When rope 1 falls sound made by nuts (hitting board) increases in frequency, indicating acceleration of rope. When rope 2 falls, the nut-hitting-board sound is periodic, due to r^2 spacing.
Note: When hanging string, first nut (on bottom of string) rests upon board. So first nut does not fall- merely used as an a position anchor.

Students are surprised to find that ball falls into cup. Nice segue into rigid body kinematics.
Instructions are taped to apparatus.
See: Slow motion video.
Located in L02, section B-2

Purpose: Show that an object’s acceleration, under the influence
of gravity, is un-effected by the objects velocity.
Cock mechanism; place pin in hole to keep cocked; place balls
on ends; release pin to eject balls.
One ball drops vertically, with zero initial velocity; other
ball launched horizontally. Balls hit floor simultaneously.
Located in L02, section B3

Purpose: Show that the effect of gravity on the launched
ball’s vertical motion is equivalent to the effect of gravity on the monkey’s
vertical motion; i.e. they fall at the same rate.
Here are some videos of this very demo. In Real time, Slow-motion, and Slow-motion face on.
Located in L02, section B3.

Some tips for setting up this demo in SC 199 (Cunniff):

Set up everything on the right side of the room (as you face the front). Clamp the target holder to the top rail of the outermost of the movable boards, about halfway across the length. (The large right angle clamp will be at an odd angle, but that’s okay. Attach the larger of the two rods to this clamp, then put the little right angle clamp about 1/2 to 2/3 of the way out on this rod.
Next, attach the smaller rod. And, finally, clamp the target holder to the small rod. Attach the metal target plate (w/optional monkey) to the magnetic release, and slowly raise the board as high as it will go.
Clamp the launcher to the front edge, right corner, of the front center table. Look through the back of the launcher to aim it. (Angle should be about 28 degrees.)
Remember to keep the trigger box disarmed while loading the launcher! And, of course, flip the switch to “Armed” before launching the ball!

Show that a penny and a feather fall at the same rate in
a vacuum.
Feather tends to stick to the walls of the container (static cling). Use styrofoam pieces instead.
Located in L02, section B2- top shelf, in large plastic container. Pump located in L02, section D1.

Measure the drop time of a small plastic ball (or any object
that isn’t so heavy that it damages the force plate upon impact).
The Pasco force probe is located 1 or 2 meters above the
floor, suspended by a ring stand, oriented with the force sensor pointing
down. A small plastic ball is pressed lightly up against the sensor and then
released. The ball lands on the force plate, resting
on the floor, directly beneath the force probe. The event is graphed using
logger pro, (in the picture above, the top graph is that of the force probe,
and the bottom the force plate). The moment of release and moment of impact are indicated on the two logger pro graphs. Time measurements are only accurate to
.02 seconds.
Force probe and labpro device is located in L35, section
B2. Force plate is located in L02 section B3.
Note: You might think that a photogate would
be the more effective and convenient way to measure the release time. But
for some reason, when the photogate is used drop times are consistently measured
to be .04 seconds too short. Which amounts to about 10% error.

Purpose: Demonstrate properties of gravitational potential
energy.
Though balls start and end at same height and with same velocity,
ball on longer track traverses path more quickly.
Located in L02, section B2

* Study acceleration of simple harmonic motion

* Measure acceleration due to gravity

* Study acceleration of elevator

* Study acceleration of cart rolling freely up and down incline.