classical physics mechanics thermodynamics waves and vibrations electromagnetism fluids/materials

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Chapter 4

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Chapter 4

Physics:Broad science dealing withthe behavior and structure

of matter and energy

ClassicalPhysics

•Mechanics•Thermodynamics•Waves and Vibrations•Electromagnetism•Fluids/Materials

Modern Physics•Relativity

•Quantum (atomic)•Nuclear•Particle•Astrophysics

MECHANICSThe branch of Physics that studies the motions of objects and how that motion relates to physical concepts (such as mass and force).

All motiondepends onthe viewpoint or the “Frame of Reference”of the observer.

MOTION: The changing of position in terms of a reference point

Distance (d): How far something travels in changing position (total)

EX. I live 5 miles from NPHS. Where do I live?

Scalar QuantityA quantity that has magnitude (size) only. No direction.Ex. Mass, time, temperature

DISPLACEMENT (∆ X or Xf-Xi)

•Change in Position Final position related to initial position *REGARDLESS OF PATH

EX. I live 5 miles from NPHS. Where do I live?

EX. I live 5 miles WEST from NPHS. Where do I live?

*∆X has both magnitude AND direction

VECTORSQuantities that have both magnitude AND direction

∆X

DIRECTIONS for VECTORS

•Positive or negative•Up or down•North, South, East or West (NE, etc…)•Coordinates (graph points)•Map gridlines (F4)•Degrees (30◦ North or 30◦ North of East)

Distance is always a positive number, but displacement can be positive OR negative.

EX. Dude walks 5 meters west (-5 units).

Dude walks 7 meters east (+7 units).

Dude walks 4 meters east (+4 units).

∆X= ___________ ?

d= __________ ?

6 meters East

16 meters

AVERAGE SPEED (v)

Def: The total distance traveled

Time to travel distance

v = d

t

OR

*SCALAR quantity

s = d

tr = d

t

SI UNITS: meters/second OR m/s

*km/hr more common

British Engineering Standard: feet/second OR ft/s

*miles/hour (mph) more common*quick convert: mph ≈ twice m/s

Conversion1 m/s = 3.6 km/h = 2.24 mi/h

1 mph = 1.609 km/hr = 0.447 m/s

Usain Bolt holds the record for the 100m dash at 9.58 seconds. Find his average speed in : a.) m/s b.) km/hr c.) mph

100 m/9.58 sec = 10.44 m/s

10.44 m/s X (7.2 km/hr) = 37.58 km/hr ( 2 m/s )

10.44 m/s X (4.5 mph) = 23.49 mph (2 m/s)

Instantaneous Speed Speed at a specific instant in time

Average VelocityHow fast AND in what direction (Vector Quantity)

Average Velocity = displacement/time

EX. The Green Racer drives 80 km west in 1 hour .

The Green Racer then drives 70 km east in 2 hours . Find the Green Racers average speed and average velocity.Speed=d/t……150 km / 3 hr ……… 50 km/hr.

Velocity= ∆X /t…..10 km west /3 hr ….3.3 km/hr west…..OR …..-10 km/3hr….-3.3 km/hr

INSTANTANEOUS VELOCITY