Mikail A. Siddiq - Raymond School

Simple Machines make work easier.  

Mikail A. Siddiq               Raymond School
                               3663 S. Wabash      
                               CHICAGO IL 60653 
                               (773) 535-1745

Objective(s):

   My objective are to show that through the use of simple machines work can    
be made easier. 

Materials Needed:

  A board about one (1) meter long and a triangular block of wood.
  A pencil sharpener, a long piece of string and a few books.
  A single fixed pulley with a string or cord.
  A few meter sticks about six. 
  A compass rose.

Strategy:

    First to show that lifting things or books manually requires more force than 
lifting through the use of simply machines. 
    Finally to measure the displacement, velocity and attempt to measure the 
amount of force used. 

Performance Assessment:

    Describe the operation of a lever.  State that a lever can be used to change 
the direction of a force. 
    Describe how a wheel and axle machine makes works easier.  Explain that 
force is gained when effort is applied to the wheel of a wheel and axle machine.       
    Identify two wheel and axle machines.

Conclusions:

    Classify simple machines as a lever, pulley, wheel or axle.    

References:

Physics: Its Methods And Meanings by Alexander Taffel, Ph.D. 

Motion and Force: Practically all of the changes we see in the world about us 
are the result of motion.  (Force: A force means simply a push, pull, or a 
lift.)  A force is being used to change the state from rest to motion.    
  Motion is controlled or changed by means of force.
Motion: is movement.  Uniform Motion: is both the speed and direction of the 
moving body remaining the same.  It is therefore motion at a constant velocity. 
Accelerated Motion: is motion with changing velocity (speeding up), the rate at 
which its speed is changing.

Displacement is a Vector: Motion generally involves a change of position of the 
object being moved.  A change of position is called a displacement.  To state 
exactly how the position of the body changed, we must also state in what 
direction it was moved.    
   Quantities such as displacement are called Vectors.  A vector is 
characterized by the fact that it has both a magnitude or size and a direction.  
Quantities having only magnitude, such as the mass or length of an object are 
called Scalars. 

Velocity and Force are Vectors: Two other important vectors related to the 
study of motion are Velocity, and Force.  To tell exactly how an object is 
moving at a given moment, we give it velocity.  By velocity we mean not only 
speed of a body but also the direction in which it is moving.  Thus, velocity is 
a vector whose magnitude is the speed of the body and whose direction is the 
direction of motion of the body.    
  It is evident that a force is a vector, since the effect a force has on a body 
depends not only on the size of the force but also on the direction in which it 
acts.  Therefore,in describing any force, we must tell not only its magnitude 
but also its direction. 

Representing a Vector:A vector is represented by an arrow drawn to some selected 
scale.  The length of the arrow shows the magnitude of the vector.  The 
direction of the arrowhead shows the direction of the vector.  To represent a 
displacement to the north of four meters, we first select a scale which, in this 
case, we take as one centimeter =one meter.  Now we draw a north - south line 
four centimeters long to represent four meters.  Finally, we put an arrowhead on 
top of this line to show the direction of the displacement. 

Energy: is the ability to do work.

   Kinetic Energy: We mean the energy that A body has because of its motion.  
Any moving body has kinetic energy because it is able to do work by moving other 
bodies. 
   M=Mass, d=Distance, F=Constant Force: The work done by the force is (Fxd).  
If (a)=is the acceleration produced by F, then F=Ma.  It follows that the work 
done is: Fd=Mad: For a body that starts from rest and is accelerated at a 
constant rate a, the speed acquired by the body after traveling a distance (d) 
is given by (V2=2ad) whence,     
                            ad=(V2)/2
Substituting this value of (ad)in (Fd)=Mad, we have:
   Fd=(MV2)/2: This quantity is defined as the kinetic energy KE of the body 
KE=1/2MV2 

    Potential Energy: A body possesses energy in a stored form that is not 
readily noticeable and is called potential.  We may define potential energy as 
the ability of a body to do work because of the relative position of its parts 
or because of its position with respect to other bodies. 
  To compute the gravitational potential energy that a body has over a selected 
base level, we simply compute the work needed to raise it from the base level to 
its actual position.  For bodies near the surface, this work is equal to the 
surface, this work is equal to the weight of the body (w) times the height it 
was lifted (h).  
  
  Therefore:

Potential Energy =w x h
and since    w=Mg
          PE  =Mgh 

Questions for the class:
(1). Describe the operation of a lever.
(2). Describe how a wheel and axle machine makes work easier.
(3). Classify simple machines as a lever, pulley, or wheel and axle machine. 
(4). Also in each example of a lever, pulley, or wheel and axle machine, tell 
     whether we are using displacement, velocity, or force or a combination of 
     each.