CH08 basic theories and math STUDENT VERSION rev

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Chapter 8

Basic Theories and Math

States of Matter (cont’d)

• By adding or removing heat, matter can change states.

Mass and Weight

• Mass

– Is the amount of matter in an object

– Size is related to mass

• Weight

– Is a force measured in pounds or grams – Is caused by gravitational pull.

• An object’s size is related to its mass.

• Size dimensions are typically stated by length, width, and height.

• Volume is the product of all three.

• Ratios can also be expressed as proportions

• Coolant is often mixed 50% water and 50% coolant This is a 1:1 ratio

• The air/fuel mixture is typically 14.7:1 This means 14.7 parts of air are mixed with 1

part of fuel

Automotive Forces

• Balanced forces are in equilibrium

• Turning forces can cause an object to rotate

• Centrifugal and centripetal forces are either away from or towards the center of a circle

• Pressure is a force applied against an object and measured in unit of force per unit of

surface area

• When forces on an object do not cancel out, they will change the object’s speed,

direction or motion, or both

• The resistance to change is called inertia

• When a forces overcomes inertia, the object gains momentum

• Speed is the distance an object travels in a set amount of time

• Calculated by dividing the distance traveled

by the time to travel the distance

• Velocity is speed in a particular direction

• Acceleration is an increase in speed

• Deceleration is a decrease in speed

Newton’s Laws of Motion

• An object at rest tends to remain at rest, and

an object in motion tends to stay in motion

• When a force acts upon an object, the

motion of the object will change

• For every action, there is an equal and

opposite reaction

• Slows or prevents motion of two objects or surfaces that touch

• Friction occurs in solids, liquids, and gases

– Good friction – brake system

– Bad friction – metal-on-metal contact in an

engine

Changing Friction

• Mechanical friction can be reduced by using bearings and lubricants

• Air resistance is reduced by improving

vehicle body design to reduce drag

• Brake system effectiveness can be either

increased or decreased by the quality of

friction components

• Work is done when a force moves a certain mass a specific distance

• Work is equal to the applied force multiplied

by the distance the object moved

Force x Distance = Work

• Work is measured in foot-pounds, watts,

Newton-meters, or joules

Work Being Performed

• Torque is a force that does work that tends

to rotate or turn things

• Torque is force times leverage

• To have torque, it is not necessary to have movement

Torque Multiplication

• Fluids conform to the shape of their

container

• Basically incompressible

• Can transmit force and motion

• Liquids exert pressure on immersed objects

• If pressure is enough the object will float

Laws of Hydraulics

• Hydraulics is the study of liquids in motion.

• Liquids are non-compressible.

• Pressure is transmitted equally in all directions.

• Hydraulics can provide a mechanical

advantage.

• Pressures and mechanical advantage are

mathematically computed.

Sample Hydraulic System

• A gas is a fluid made up of particles that are

in constant, random motion

• Gases fill their container

• Two gases sharing a container will mix –

this is called diffusion

• The kinetic energy of a gas increases as the temperature increases

• The higher the temperature of a gas, the

higher the volume

• Also called low or negative pressure.

• Perfect vacuum is 29.9 inches of mercury

• Temperature is an indication of an object’s kinetic energy

• Heat is measured in Btu, calories, or joules

• Anything that gives off heat is a source of heat

Methods of Heat Transfer

The pH Scale

• Used to measure how acidic or basic a solution is

• Scale is from 0 to 14

• Distilled (pure) water is 7

• Acids are between 0 and 7

• Bases are between 7 and 14

Reduction and Oxidation

(Redox)

• Oxidation is when a substance combines with oxygen.

• Rapid oxidation produces heat.

• The addition of hydrogen atoms or electrons is reduction.

• Both occur simultaneously.

• Redox is any reaction in which electrons are transferred.

Electricity and Electromagnetism

• All electrical effects are caused by electrical charges – positive and negative

• Protons carry a positive charge

• Electrons carry a negative charge

• Electricity and magnetism are intertwined and inseperable

• All magnets have a North and South pole.

• A magnetic field exists between the poles

• A magnetic field is generated around a

current carrying conductor

• Increasing the current increases the strength

of the magnetic field

Producing Electrical Energy

• Moving a conductor through a magnetic field produces electricity

• This is how the vehicle’s generator and

power generation plants produce electricity