Mr. Bouyer

Day 1 | Day 2 | Day 3 | Lab | Vocabulary Test

Simple machine Inclined plane Wedge Screw Lever	Fulcrum 1st class lever 2nd class lever 3rd class lever Pulley	Fixed pulley Movable pulley Pulley system Wheel and axle Compound machine

Machines:   change the size and direction of a force.

Machines make work easier or faster, but never produce more work than is put into them. In fact, because of friction, more work is put into a machine than comes out!

What type of simple machine is a knife?

Types of machines: simple or compound.

Simple machines do work with one movement.

 

There are 6 simple machines.

Inclined plane a slanted surface used to raise an object.

Work is made easier because the effort force moves over a greater distance.
Mechanical advantage is equal to the length of the plane divided by its height.

Wedge a moving inclined plane.

Force is multiplied since it is applied to a wide area and exerted over a small area.
The "sharper" the wedge, the greater the mechanical advantage.

Screw man inclined plane wrapped around a cylinder.

Multiplies an effort force by acting through a long effort distance.
The closer the threads on a screw, the greater the mechanical advantage.

Homework Assignment 261:
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criteria

1. Name the simple machines represented by each tool pictured at right.
2. To load a 55 gallon drum onto his truck, a worker lays a couple of 4 meter planks off the edge of the truck bed which is one meter off the ground. The drum, which has a weight of 5000 Newtons, is rolled up the planks into the truck.
   1. What simple machine did the worker use?
   2. What is the mechanical advantage of this machine?
   3. As you know, any machine has friction. What type of friction is involved in this machine?
   4. How much work was done using the machine?
   5. How much work would have been done if the worker had lifted the drum directly from the ground to the truck bed?

3. Go to the Allmetal Screw Products Corp to find the information needed for the following questions.
   1. How many threads per inch are found on a 7/8 inch "unified coarse thread" fastener?
   2. How many threads per inch are found on a 7/8 inch "unified fine thread" fastener?
   3. Which of the two fasteners above has the greatest mechanical advantage?

Day 2

"Give me a place to stand and I will move the Earth."

What type of lever is a baseball bat?

Lever a bar which can move freely around a fixed position, or fulcrum.
First-class lever
• Fulcrum is between EF and RF
• Multiplies EF and changes its direction

 

Experiment with a first-class lever.  

Second-class lever

• RF is between fulcrum and EF
• Multiplies EF, but does not change its direction

Third-class lever

• EF is between fulcrum and RF
• Does not multiply force
• Multiplies the distance the effort force travels


To calculate the mechanical advantage of any lever, divide the effort arm length by the resistance arm length.

Pulley a belt, rope, or chain wrapped around a wheel.

Fixed pulley
• Does not multiply force.
• Changes the direction of the effort force.
• Mechanical advantage is equal to one.

Movable pulley

• Multiplies effort force but cannot change direction of the effort force.
• Mechanical advantage is the effort distance divided by the resistance distance.

Pulley system

• A combination of fixed and movable pulleys.
• Mechanical advantage is equal to the number of supporting ropes.

 

Experiment with pulleys.  

Wheel and axle a lever that rotates in a circle around an axle.

Two wheels of different sizes connected - the axle being the smaller wheel.
EF applied to the wheel is multiplied at the axle.

 

With your table, do the following: Given a 100 gram mass, a spring scale, one small pulley, and a piece of twine - write a detailed set of procedures for an experiment to prove that a fixed pulley does not multiply an effort force, while a movable pulley does. When your table has the procedures, ask your facilitator for the equipment and perform the experiment.

Day 3

Compound machines

combinations of two or more simple machines.

Physical Science

A knife is an example of a wedge.

A baseball bat is an example of a third-class lever.

Scissors are made up of two first-class levers.