Return to Physics IndexMikail A. Siddiq - Raymond SchoolSimple Machines make work easier.

Mikail A. Siddiq Raymond School

3663 S. Wabash

CHICAGO IL 60653

(773) 535-1745Objective(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 Meaningsby 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 (V^{2}=2ad) whence,

ad=(V^{2})/2

Substituting this value of (ad)in (Fd)=Mad, we have:

Fd=(MV^{2})/2: This quantity is defined as the kinetic energy KE of the body

KE=1/2MV^{2}

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.