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Introduction to KinematicsIntroduction to Kinematics

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MechanicsMechanics

Mechanics is the study of motion. There are two main branches of

Mechanics:1. Kinematics

2. Dynamics

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KinematicsKinematics

Kinematics is the branch of physics that deals with describing motion without making reference to the things that cause the motion.

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DynamicsDynamics

Dynamics is the branch of mechanics that deals with both the motion and the causes of the motion of an object.

Quantitative vs Qualitative Quantitative vs Qualitative ObservationsObservations

Qualitative Observations involve describing something using words and not number.– Examples: a tall man; a heavy man; a flexible,

transparent, and red ruler.

Quantitative Observations involve describing things using measurements.– Examples: 125 kilograms, 199 centimetres, 9.6

seconds

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Quantitative Observations and Quantitative Observations and MeasurementsMeasurements

Quantitative Observations are more accurate than Qualitative Observations.

Measurements must have at least two parts. They must have a number and a unit.– Examples: 35 g, 56.25 mg

There are two different types of Quantitative Observations: Scalars and Vectors.

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ScalarsScalars

Scalars have only a magnitude and a unit but do not have a direction.– Examples: 75 kg, 42 pounds, 12 cm,

3300 Ohms.

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VectorsVectors

Vectors are directed measurements.Vectors include both a magnitude (size), a

unit, and a direction.– Examples: 8.5 km [N], 13 m [down]

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Comparison of Vectors and ScalarsComparison of Vectors and Scalars

Vectors Scalars

Displacement Distance

Velocity Speed

Acceleration Acceleration

Time

Mass

Energy

Force

Electric Field

Voltage

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SI Units of Measurement: SI Units of Measurement: Base UnitsBase Units

Name Symbol Unit of

metre m length

kilogram kg mass

second s time

ampere A electric current

kelvin Kthermodynamic temperature

mole mol amount of substance

candela cd luminous intensity

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SI Units of Measurement: SI Units of Measurement: Derived UnitsDerived Units

By combining the seven base units, all other quantities can be measured.

For instance, volume can be measured in m³, speed can be measured using m/s, and force can be measured in kg·m/s².

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SI Units of Measurement: SI Units of Measurement: PrefixesPrefixes

Factor Name  Symbol

1024 yotta Y

1021 zetta Z

1018 exa E

1015 peta P

1012 tera T

109 giga G

106 mega M

103 kilo k

102 hecto h

101 deca da

Factor Name  Symbol

10-1 deci d

10-2 centi c

10-3 milli m

10-6 micro µ

10-9 nano n

10-12 pico p

10-15 femto f

10-18 atto a

10-21 zepto z

10-24 yocto y

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Uniform MotionUniform Motion

Uniform Motion is motion at a constant speed in a straight line.– Uniform motion is motion that does not

undergo any acceleration.– Uniform motion does not undergo a change in

speed or change the direction of motion (it does not turn).

– This is the easiest motion to study and can create an inertial reference frame.

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Formula for Uniform MotionFormula for Uniform Motion

t

dV

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Units for VelocityUnits for Velocity

The standard units for velocity are m/s.km/h are also used for velocity.Velocity must include a direction. The

direction should be recorded in brackets; ie. [N 20° E].

The direction may also be expressed as 20° East of North or North 20° East.

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Converting from km/h to m/sConverting from km/h to m/s

The best way to convert from km/h to m/s is to make two separate conversions.

Change kilometres to metres and then convert hours to seconds.

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Uniform Motion QuestionUniform Motion Question

Find the speed if someone travels 50.0 km in two hours and 15 minutes. Leave your answer in both m/s and km/h.

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smv

hkmv

h

kmv

t

dv

/17.6

/2.22

)25.2(

)0.50(

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Final AnswerFinal Answer

Therefore the speed required to travel 50.0km in 2 hours and 15 minutes is 22.2km/h which is also 6.17 m/s.

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Try Another QuestionTry Another Question

A man walks north at 3.0 km/h for 4 hours.The man then speeds up and runs at

12.3km/h for 1.5 hours.Find the total displacement.Find the average velocity.

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