Lever Action
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Jimmy Spieth 8a
2-22-05
8th Grade Science Project
Title:
Lever Action
State the problem:
In this project we have a board (lever board) that contains three
individual levers: A first class lever, a second class lever, and a third class
lever. Which lever of the three might be called a mechanical disadvantage?
In other words, which lever makes it harder to lift objects.
Hypothesis:
I believe that the third class lever would be the mechanical
disadvantage because when the effort (input force) is between the
load and pivot (fulcrum), the load is always heavier. The closer the
input force is to the pivot point, the heavier the load becomes.
Background:
Levers are one of the basic tools that were probably used in
prehistoric times. Levers were first described about 260 BC by the ancient
Greek mathematician Archimedes.
A lever is a simple machine that makes work easier for use. A lever is
a rigid bar or rod that can pivot about a fixed position. The fixed position is
called a fulcrum. A lever can change the strength or direction of a force in
order to do work. When a person does work on a lever, he or she is
transferring energy to the lever. The lever then uses that energy to perform
work on another object. The lever, therefore, transfers its energy to the
object. Work is performed whenever a force moves an object. The work a
person does on a lever is called the input work (effort force) and the work done by the lever is called the output work (resistance force). The output work can never be greater than the input work. The lever does not add energy to the system, it simply transfers energy in an efficient way. This is commonly known as mechanical advantage.
Levers can be divided into three classes, based on the location of the
pivot (fulcrum).
The first class lever are those where the fulcrum is between the effort force and the resistance force
(load). Examples of first class levers include a
crowbar or a seesaw.
The second class lever are those where the fulcrum is at the end of the bar or rod and the load is between the effort force and the fulcrum. Examples of second class levers include a wheelbarrow or a bottle opener.
The third class lever are those where the fulcrum is
at the same end as the effort force. In these levers, the
resistance distance is actually greater than the effort
distance. Examples of third class levers include
fishing poles, tongs, and cranes.
Procedures:
List of materials used:
Berkley digital scale
14″ accessory rod
3/4″ Birch plywood 2 x 2
Three 1 Д x 2 oak boards
Two 2 Ð…” x 2 oak boards
2 length 1″ oak doll rod
5/16″ steel rod with 2 nuts
Eight zinc plated eye hooks
11 zinc plated screws
Wood stain and polyurethane
One 2 Ð… lb. weight plate
Once the assembly of the main board is completed by using the
materials mentioned above, the individual levers can be labeled; first class
lever, second class lever, and third class lever. Each lever than has four
effort locations (labeled A, B, C, and D) where the push or pull gauge can
measure individual test proceedings during the experiment.
The experiment is broken down into three phases. Each phase
representing a individual class lever. The board has to be on a level surface.
The first phase is conducted with the first class lever. Place a 2 Ð… lb. weight
plate on the load pedestal. The lever by itself weighs 0.7 lbs. Next, take the
Berkley scale with the 14″ accessory rod and place it in the position “A”
notch. Make sure to turn the scale on by pressing the on button first. This
also calibrates the scale. A reading of 0.0 should be displayed. Now apply
pressure with the scale in a downward force til the lever balances itself in
the horizontal