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Energy

Chapter 8 main concepts

Vocabulary

Vocabulary

Vocabulary

Vocabulary

Vocabulary

Concepts - WORK

Concepts - POWER

Concepts – KINETIC ENERGY

Concepts – POTENTIAL
ENERGY

Concepts – POTENTIAL
ENERGY

Concepts – CONSERVATION
of ENERGY

Concepts – CONSERVATION
of ENERGY

On-line Resources

Example - WORK

Example-CONSERVATION of
ENERGY

Example – POWER

Example– KINETIC ENERGY

end

Energy

Conceptual Physics

Chapter 8

September 2004

End of slide show, click to exit.

Energy

Conceptual Physics

Chapter 8

September 2004

Chapter 8 main concepts

Work

Force time displacement

Power

Work divide by time

Energy

The ability to do work

Kinetic Energy

The energy of motion

Potential Energy

Energy of position or stored energy

Conservation of Energy

Energy cannot be created or destroyed

Efficiency

Ratio of work output to work input

Vocabulary

Power

pow·er  n.

The rate at which work is done,
expressed as the amount of work per unit time and commonly measured in units
such as the watt and horsepower.

[Middle English, from Old French pooir,
to be able, power, from Vulgar Latin *pot re, to be able, from potis, able,
powerful. See poti- in Indo-European Roots.]

Vocabulary

Work

work  n.

The transfer of energy from one
physical system to another, especially the transfer of energy to a body by
the application of a force that moves the body in the direction of the force.

It is calculated as the product of the force
and the distance through which the body moves and is expressed in joules,
ergs, and foot-pounds.

[Middle English, from Old English
weorc. See werg- in Indo-European Roots.]

Vocabulary

Energy

en·er·gy  n. pl. en·er·gies

The capacity of a physical system to do
work.

[French énergie, from Late Latin energ
a, from Greek energeia, from energos, active  : en-, in, at; see en-2 +
ergon, work; see werg- in Indo-European Roots.]

Vocabulary

Kinetic

ki·net·ic  adj.

Of, relating to, or produced by motion.

Relating to or exhibiting kinesis.

[Greek k n tikos, from k n tos, moving, from k nein, to move. See kei-2 in
Indo-European Roots.]ki·net i·cal·ly adv.

Vocabulary

Potential

po·ten·tial  adj.

The work required to move an amount of
mass from a reference point to a designated point in a static electric,
magnetic, or gravitational field; potential energy.

[Middle English potencial, from Old
French potenciel, from Late Latin potentia lis, powerful, from Latin
potentia, power, from pot ens, potent- present participle of posse, to be
able. See potent.]

Concepts - WORK

WORK = Force x displacement

UNITS

(force)x(distance)

or (mass)x(distance2)/(time)2

SI Units

Joule = N•m = kg•m2/sec2

English Units

lb•ft (pound feet or foot pounds)

Conversions

1 Joule = 0.74 lb•ft

Expression

W=F∆d

Concepts - POWER

POWER = (WORK) / (ELAPSED TIME) “work
per unit time”

UNITS

(force)x(distance)/(time)

or (mass)x(distance2)/(time)3

SI Units

Watt = Joule/sec = N•m/sec = kg•m2/sec2

English Units

lb•ft/sec (pound feet per second)

Conversions

1 kW = 1,000 Watts

1 horsepower = 550 lb•ft/sec = .75 kW

Expression

P = W/∆t

Concepts – KINETIC ENERGY

KINETIC ENERGY = ½ (mass) x (speed)2

UNITS

(mass)x(distance)2/(time)2

SI Units

Joule = N•m = kg•m2/sec2

English Units

lb•ft (pound feet or foot pounds)

Conversions

1 Joule = 0.74 lb•ft

Expression

W=F∆d

Concepts – POTENTIAL
ENERGY

POTENTIAL ENERGY = Force x displacement

UNITS

(force)x(∆distance)

or (mass)x(distance)2/(time)2

SI Units

Joule = N•m = kg•m2/sec2

English Units

lb•ft (pound feet or foot pounds)

Conversions

1 Joule = 0.74 lb•ft

Expression

∆PE=mg∆h

Concepts – POTENTIAL
ENERGY

POTENTIAL ENERGY = Force x displacement

Only the displacement in the direction
the force is acting is considered.

When considering an object pushed up a
frictionless incline, only the vertical distance is considered because there
is no force resisting the horizontal component of the motion. In this type of
case the PE is simply the weight of the object time the height it is lifted.

Expression

∆PE=mg∆h

Concepts – CONSERVATION
of ENERGY

Conservation of Energy

Energy cannot be created or destroyed!

Concepts – CONSERVATION
of ENERGY

Conservation of Energy

∆KE = ∆PE

or

KE0 + PE0 = KE1
+ PE1

On-line Resources

Sports Figures – Perpetual Motion

Tony Hawk Skateboarding

http://sportsfigures.espn.com/sportsfigures/lp_perpetual_motion03.htm

Simulations

http://zebu.uoregon.edu/1999/ph161/l5.html

Example - WORK

Weight of block is  ___ , Frictionless Ramp is ____ high, ____

How much force required to push block
up ramp?

Example-CONSERVATION of
ENERGY

Given ∆h,

Solve for velocity v at the bottom of
the arc

Example – POWER

Example– KINETIC ENERGY

end

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