6 - Energy, Work, Power

Energy

ability to do work

Power

rate of doing work

Work

the energy transferred to or from a system by a force that acts on it

Work

In physics, ____ represents…

a measurable change in a system, caused by a force.

no work

A pushing force does ______ if the box does not move.

work

A pushing force does ___ if the box moves even a little.

Force x Distance

Work formula:

• Joules = Newton • meter

• lb• foot

Units of Work: (2)

W = F(cos 0)•d

Work at an angle FORMULA:

Energy

is the ability to do work

Energy

may exist mechanical, thermal, electrical, nuclear, chemical, and other forms

Mechanical energy

The energy which is possesed by an object due to its motion

• Kinetic

• Potential

2 Types of Mechanical Energy:

Kinetic

energy in motion

Potential

an object can store energy

• as the result of its position or elastic source

• Gravitational PE

• Chemical PE

• Elastic PE

Forms of POTENTIAL ENERGY: (3)

Gravitational Potential Energy (GPE)

the energy possessed by an object due to its position

• It is determined by the height of an object above the earth’s center of gravity

GPE = mass • g • height

GPE formula:

Chemical Potential Energy

energy possessed by atoms/molecules of a substance

• is released or changed into other forms when a substance is involved in a chemical reaction.

Elastic Potential Energy

energy possessed by an object,

• like a spring,

• or any other elastic material due to its condition

Kinetic Energy

the energy in motion

△KE = ½ m • v²

KE formula:

Power

is the rate of using energy.

Power

It simply the energy exchanged per unit time, or how fast you get work done.

P = W / t

• F • d / t

• m•g•h / t

Power formula:

• kilowatt

• horsepower

Units of Power:

• 1000 watts

• 1.34 hp

1 kw = ______ watts

= ______ hp

• 746 watts

• 550 ft.lb/s

1 hp = ______ watts

= ______ ft.lb/s