Lever Action

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:

(1) Berkley digital scale

(2) 14" accessory rod

(3) 3/4" Birch plywood 2' x 2'

(4) Three 1 Ð..." x 2' oak boards

(5) Two 2 Ð..." x 2' oak boards

(6) 2' length 1" oak doll rod

(7) 5/16" steel rod with 2 nuts

(8) Eight zinc plated eye hooks

(9) 11 zinc plated screws

(10) Wood stain and polyurethane

(11) 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