**Energy - **The "something" that enables work
to be done.

**Kinetic energy - **energy of motion.

We usually define **mechanical energy **as the sum of all the kinetic
and potential energy. Since the energy of an object must be conserved,
the kinetic energy used to place a book on a shelf is stored in the book
as potential energy, all the while the mechanical energy staying constant.

**Work **is the amount of energy required to move an object, or released
by the motion of an object, a certain distance; motion must be in the same
direction of the applied force. If work is done on an object by its surroundings,
the work is positive. When work is done by an object on its surroundings,
the work is negative. The sign of the work indicates the direction of motion
of energy.

The **Work-energy theorem **states that work equals the change in
kinetic energy

**Work **is the applied force multiplied by the distance traveled,
both in the same direction.

Any device that makes work easier to perform is known as aUSCS --> ft^{.}lb; calorie/CalorieSI --> N^{.}m or Joule (J)

The force applied to the machine is called the** effort force. **The
force applied by the machine is called the** resistance force.**

For example to raise a** 100 N **box** 1 m, 100 J **of work must
be done. If you were to lift the box straight up, you would have to exert
**100
N **of **effort force** to move the **100 N resistance force
**of
the box’s weight. If you used a machine such as a ramp, you may be able
to reduce your **effort force **to** 50 N **as you push the box up
the ramp, but you would have to push the box** 2 m. **This is because
**100 J **of work is still required to get the job done. The machine
just makes it easier (in terms of force you must exert.)

**Work input **is the amount of work (energy) that goes into the
machine. This work comes from the force that is applied to the machine,
effort force.
**Work output **is the amount of work (energy) that comes out of
the machine. This work is used to overcome the resistance force.

Machines cannot increase the amount of work that is put into them. This
would violate the *law of conservation of energy*. The work input
must always be larger than or equal to the work output in order for the
machine to work properly. If the work input equals the work output the
machine is said to be ideal, or 100% efficient.

The efficiency of a machine is defined as the ratio of work output to work input.

The closer the work out is to the work in, the more efficient the machine is.

Another important measure of a machine is the number of times it changes
the effort force. This is called the **mechanical advantage **of the
machine.

There are two main categories of simple machines:** the inclined plane
and the lever. **All simple machines fall into one of the two categories.
With each type of machine is an equation for its** ideal mechanical
advantage (IMA)**, a 100% efficient machine. An ideal machine assumes
the absence or neglecting of friction and other extraneous forces. The
basic equation for IMA is

Look at each of the IMA equations below and identify how each part corresponds with the basic equation.

**Inclined planes**

**The ramp: **an incline used to assist lifting

**The wedge: **Double incline that may move

**The screw: ** incline (threads) wrapped around a post

**Levers**

1) First class -Fulcrum is between effort and resistance forces: shovel.2) Second class -Fulcrum at one end, effort force is at other end, resistancein middle: Wheelbarrow.3) Third class -Fulcrum at one end, resistance force at other end, effort inthe middle: Rake, broom.

**The pulley: **the pulley is the fulcrum, the strands are the effort
and resistance arms.