EnergyInvestigation 3

By: Vinny McComb and Marisol CalderonJosh Coffey

History Of EnergyFrom Greek energeia meaning “activity.”Not part of original Newtonian mechanics.Introduced into physics by Helmholtz in 1847.

Defining Property of Energy

The total energy of an isolated system does not change with time.

Types of Energy Kinetic Energy

Formula:

EK = mv2/2

Potential Energy Formula:

EP = mgh

Kinetic energy If an object is moving

then it is capable of doing work. The object has energy of

motion (kinetic energy). The kinetic Energy of an

object is dependant on the amount of mass and sped of the object and its is equal to half of the mass x speed squared Kinetic Energy= .5

(MassxSpeedSquared)

Potential EnergyAn object can have energy due to its position

this is called potential energy!At a resting state the object only has potential to

do work.A good example is an object like a compressed

spring that has the “potential” to do work (spring upwards).

Potential Energy= Weight x Height

WorkQuantity of force x Distance= Work

An example of this is if you have a bowling ball and you want to shoot it up in the air 2 ft., it wont require nearly as much work as trying to shoot a bowling ball 20 ft.

Work occurs when one moves an object against the Earths gravitational pull.

The heavier the load requires more work depending on the distance the

The Measurement of “Work”

When the measurement of force you combine the unit of force (Newton) with the units of distance (Meters)

MxN=Joules1 Joule of work is done when one Newton of

force is exerted over the distance of one meter.

Power Power= Work done/Time

interval An example of when you need

to think of power is when you carry a load up stairs, you do the same amount of work whether you run up the stairs or walk up the stair. Than why are you more tiered when you run up the stairs in a few seconds rather than walk in a few minutes?

This is the thought of work done over time or Power.

Power (Continued)Power is simply energy exchanged per unit time,

or how fast you get work done (Watts = Joules/sec)

One horsepower = 745 WPerform 100 J of work in 1 s, and call it 100 WRun upstairs, raising your 70 kg (700 N) mass 3

m (2,100 J) in 3 seconds 700 W output!Shuttle puts out a few GW (gigawatts, or 109 W)

of power!

Energy is ConservedThe total energy (in all forms) in a “closed” system

remains constantThis is one of nature’s “conservation laws”

Conservation applies to: Energy (includes mass via E = mc2) Momentum Angular Momentum Electric Charge

Conservation laws are fundamental in physics, and stem from symmetries in our space and time Emmy Noether formulated this deep connection cedar.evansville.edu/~ck6/bstud/noether.html

Machines A device by which a small

force applied at convenient point can be used to overcome a large force at some other point. The force overcome by a machine is many times greater than the input force, the energy or work output can never be greater than the input energy or work. In

Work input=Work output

Types of Machines3 Types of machines

The lever, the pulley, and the inclined plane

Also known as wheel and axle, the wedge, and the screw are modifications of the three simple machines.

3 types of Levers

Pulleys Two types of pulleys

Fixed pulleys Moveable pulleys Are simple machines that

consist of a rope that slides around a disk, called a block. Their main function is to change the direction of the tension force in a rope.