7/27/2019 Chapter 8 - Nick Collico

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Chapter 8 Power point

A PowerPoint produced by Nick

Collico

Block 8

Freshman Physics

Mr. Rhodes

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Energy

Examples of energy. When we consider the quantityforce X distance, we are talking

about work.

Two things enter into every

case where work is done. 1) the

application of a force and 2) themovement of something by that

force.

Work = force x distance or W =

Fd

Work falls in two categories The unit of measurement for

work combines a unit of force,

N, with a unit of distance being

M, the result of this is a joule.

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Power

Some examples of

power

Power is the rate at which work

is done. It equals the amount of

work done by dividing the time

interval during which the work

is done.

Power = work done over timeinterval

The unit of power is joule per

second, also known as the watt,

in honor of James Watt.

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Mechanical Energy

Some examples of

mechanical energy

Energy enables an object to do

work

Mechanical energy- the energy

due to position of something, or

the movement of something

Mechanical energy can be in theform of either potential energy

or kinetic energy, or the sum of

the two.

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Potential energy

Some examples ofpotential energy

An object may store energy byvirtue of its position

The energy that is stored iscalled potential energy

Chemical energy in fuels is also

potential energy Work is required to elevate

objects against the earthsgravity

The potential energy due toelevated positions is called

gravitational energy Gravitational potential energy =

weight x height

PE = mgh

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Kinetic energy

Some examples ofkinetic energy

If an object is in moving, then itis capable of doing work

It has energy of motion, orkinetic energy

The kinetic energy of an object

depends on the mass of theobject as well as its speed

Kinetic energy = mass xspeed squared

Net force x distance = kineticenergy

Fd = mv squared Whenever work is done, energy

changes. This is the work-energy theorem

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Conservation of energy

Some examples of conservation of

energy

The study of the various forms

of energy and the

transformation from one form

into another led to one of the

greatest generalizations in

physicsthe law ofconservation of energy

Energy cannot be created or

destroyed

It can be transformed from one

form to another

The welding of an atomic nuclei

is called thermonuclear fusion

and will be covered later.

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Machines

Some machines A machine is a device used tomultiply forces or simply to change

the direction of forces

When we do work on the end of a

lever, the other end does not work

on the load

(force x distance) input = (force x

distance) output

The pivot point is also known as the

fulcrum

The ratio of the output force to the

input force for a machine is the

mechanical advantage

A pulley is basically a kind of lever

that can be used to change the

direction of a force.

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Efficiency

Some examples of

efficiency

An ideal machine would have

100% efficiency

In any machine, some energy is

transformed into atomic or

molecular kinetic energy

making the machine warmer Efficiency can be expressed at

the ratio of useful work output

to total work input

Efficiency = useful work output

divided by total work input

Efficiency = actual mechanical

advantage divided by

theoretical mechanical

advantage

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Energy for life

Some examples of

energy for life

Every living cell in every

organism is a machine. Like any

machine, living cells need an

energy supply

Only green plants and certain

one-celled organisms can makecarbon dioxide to combine with

water to produce hydrocarbon

compounds such as sugar. This

process is known as

photosynthesis and requires an

energy input which normallycomes from the sun

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Review of chapter

Some simple

machines ETC.

When a constant forces moves

and object in the direction of

the force, the work done equals

the product of the force and the

distance the object is moved

Power is the rate at which workis done

The energy of an object enables

it to do work

Mechanical energy is due to the

position of something (potential

energy) or the movement of

something (kinetic energy)

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Review of Chapter, Continued

Some simple

machines

The law of conservation of

energy states that energy

cannot be created or destroyed

Energy can be transformed

from one form to another

A machine is a device formultiplying force or changing

the direction of force

The lever, pulley, and inclined

plane are simple machines

The useful work output of amachine is less than the total

work input

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