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Motion
Introduction Section 0 Lecture 1 Slide 1
Lecture 3 Slide 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Motion
Introduction Section 0 Lecture 1 Slide 2
Lecture 3 Slide 2
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
PHYSICS OF TECHNOLOGY Spring 2009 Assignment Sheet
*Homework Handout
Date Day Lecture Chapter Homework Due Jan 5 6 7 9
M T W F*
Class Admin: Intro.Physics Phenomena Problem solving and math Units, Scalars, Vectors, Speed and Velocity
1 App. B, C 1 2
-
Jan 12 14 16
M W F*
Acceleration Free Falling Objects Projectile Motion
2 3 3
1
Jan 19 21 23
M W F*
Martin Luther King Newton’s Laws Mass and Weight
No Class 4 4
2
Jan 26 28 29 30
M W Th F
Motion with Friction Review Test 1 Circular Motion
4 1-4 1-4 5
3
Feb 2 4 6
M W F*
Planetary Motion and Gravity Energy Harmonic Motion
5 6 6
4
Feb 9 11 13
M W F*
Momentum Impulse and Collisions Rotational Motion
7 7 8
5
Feb 16 17 18 19 20
M Tu W H F*
Presidents Day Angular Momentum (Virtual Monday) Review Test 2 Static Fluids, Pressure
No Class 8 5-8 5-8 9
-
Feb 23 25 27
M W F*
Flotation Fluids in Motion Temperature and Heat
9 9 10
6
Mar 2 4 6
M W F*
First Law of Thermodynamics Heat flow and Greenhouse Effect Climate Change
10 10 -
7
Mar 9-13 M-F Spring Break No Classes Mar 16 18 20
M W F*
Heat Engines Power and Refrigeration Electric Charge
11 11 12
8
Mar 23 25 26 27
M W H F*
Electric Fields and Electric Potential Review Test 3 Electric Circuits
12 13 9-12 13
-
Mar 30 Apr 1 3
M W F
Magnetic Force Review Electromagnets Motors and Generators
14 9-12 14
9
Apr 6 8 10
M W F*
Making Waves Sound Waves E-M Waves, Light and Color
15 15 16
10
Apr 13 15 17
M W F*
Mirrors and Reflections Refraction and Lenses Telescopes and Microscopes
17 17 17
11
Apr 20 22 24
M W F
Review Seeing Atoms The really BIG & the really small
1-17 18 (not on test) 21 (not on test)
No test week 12
May 1 F Final Exam: 09:30-11:20am
Motion
Introduction Section 0 Lecture 1 Slide 3
Lecture 3 Slide 3
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Units of Motion
Motion
Introduction Section 0 Lecture 1 Slide 4
Lecture 3 Slide 4
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What Do We Need To Measure?
What is the minimum about things we need to know?
Where things are—a length, LWhen things are there—a time, T
How thing interact with gravity—a mass, MHow things interact with E&M—a charge, Q
How thing inter act with weak nuclear forceHow things interact with strong nuclear force
Motion
Introduction Section 0 Lecture 1 Slide 5
Lecture 3 Slide 5
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Describing Motion
Position—where you are in space (L-meter)
Speed—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast speed is changing with time (LT-2 or m/s2)
Motion
Introduction Section 0 Lecture 1 Slide 6
Lecture 3 Slide 6
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Units of Motion
Need a distance unit: m, cm, mm, km ft, in, mi
light years, furlongs
Need a time unit: sec, min, hr, day, yearms, ns, fsfortnights
Speed: A distance divided by time (DT-1)m/s, mi/hr, mm/yr, furlongs/fortnight
Acceleration: A distance divided by time squared (DT-2)A speed divided by time (DT-2)m/s2, mi/hr2, mm/yr2, furlongs/fortnight2
Motion
Introduction Section 0 Lecture 1 Slide 7
Lecture 3 Slide 7
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Examples of Distance Units
Consider the lowly penny:
Value Notes on units Scientific notation 0.75 in “natural unit” 7.5 · 10-1 in 2 cm “natural” unit,
metric unit (note prefix) 2 cm
0.02 m SI unit, metric unit 2 · 10-2 m
0.00002 km metric unit (note prefix) 2 · 10-5 km
0.000012 mile 1.2 · 10-5 mile
0.01 fathom “odd” unit 1 · 10-2 fathom
0.000000000000000000002 light year “odd” unit 2 · 10-20 light year
0.000000002 angstrom “odd” unit 2 · 10-8 angstrom
Motion
Introduction Section 0 Lecture 1 Slide 8
Lecture 3 Slide 8
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Dimensions of Motion
Distance: Dimensions; (L)
ScalarSymbol: dUnits: m, cm, km, in, ft, light years, furlongs
Time: Dimensions; (T)ScalarSymbol: tUnits: s (or sec), min, hr, day, year, ms, ns, fs, fortnights
Speed: A distance divided by timeDimensions; (LT-1) ScalarSymbol: sUnits: m/s, mi/hr, mm/yr, furlongs/fortnight
Acceleration: A distance divided by time squared A speed divided by time
Dimensions; (LT-2) ScalarSymbol: aUnits: m/s2, mi/hr2, mm/yr2, furlongs/fortnight2
Motion
Introduction Section 0 Lecture 1 Slide 9
Lecture 3 Slide 9
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Speed and Velocity
Motion
Introduction Section 0 Lecture 1 Slide 10
Lecture 3 Slide 10
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What Is Speed?
Speed is how fast something is moving.– Speed is always some distance divided by some time.– The units of speed may be miles per hour, or meters
per second, or kilometers per hour, or inches per minute, etc.
Rate is one quantity divided by another quantity.– For example: gallons per minute, pesos per dollar,
points per game.– So average speed is the rate at which distance is
covered over time.
Motion
Introduction Section 0 Lecture 1 Slide 11
Lecture 3 Slide 11
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Average speed is total distance divided by total time.
Instantaneous speed is the speed at that precise instant in time.– It is the rate at which distance is being covered at a
given instant in time.– It is found by calculating the average speed, over a
short enough time that the speed does not change much.
What Is Speed?
average speed = distance traveled
time of travel
Motion
Introduction Section 0 Lecture 1 Slide 12
Lecture 3 Slide 12
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Average Speed
Kingman to Flagstaff:120 mi 2.4 hr
= 50 mphFlagstaff to Phoenix:140 mi 2.6 hr
= 54 mphTotal trip:120 mi + 140 mi
= 260 mi2.4 hr + 2.6 hr
= 5.0 hr260 mi 5.0 hr
= 52 mph
Motion
Introduction Section 0 Lecture 1 Slide 13
Lecture 3 Slide 13
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Instantaneous Velocity
Instantaneous velocity is a vector quantity having:a size (magnitude) equal to the instantaneous speed at a given instant in time, and a direction equal to the direction of motion at that instant.
Motion
Introduction Section 0 Lecture 1 Slide 14
Lecture 3 Slide 14
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Instantaneous Speed: a car traveling on a local highway
A steep slope indicates a rapid change in velocity (or speed), and thus a large acceleration. A horizontal line has zero slope and represents zero acceleration.
Motion
Introduction Section 0 Lecture 1 Slide 15
Lecture 3 Slide 15
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What Does a Speedometer Measure?
The speedometer tells us how fast we are going at a given instant in time.
A speedometer measures instantaneous speed.
(In a moment, we’ll see why a speedometer doesn’t measure velocity.)
Motion
Introduction Section 0 Lecture 1 Slide 16
Lecture 3 Slide 16
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Average speed?Instantaneous speed?
The speed limit indicates the maximum legal instantaneous speed.
To estimate the time a trip may take, you want to use average speed.
Which quantity is the highway patrol more interested in?
Motion
Introduction Section 0 Lecture 1 Slide 17
Lecture 3 Slide 17
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Velocity
Velocity involves direction of motion as well as how fast the object is going.– Velocity is a vector quantity.– Vectors have both magnitude and direction.– Velocity has a magnitude (the speed) and also a direction
(which way the object is moving).
A change in velocity can be a change in the object’s speed or direction of motion.
A speedometer doesn’t indicate direction, so it indicates instantaneous speed but not velocity.
Motion
Introduction Section 0 Lecture 1 Slide 18
Lecture 3 Slide 18
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
YesNo
At position A, the car has the velocity indicated by the arrow (vector) v1.
At position B, the car has the velocity indicated by the arrow (vector) v2, with the same magnitude (speed) but a different direction.
A car goes around a curve at constant speed. Is the car’s velocity changing?
Motion
Introduction Section 0 Lecture 1 Slide 19
Lecture 3 Slide 19
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Changing Velocity
A force is required to produce a change in either the magnitude (speed) or direction of velocity.
For the car to round the curve, friction between the wheels and the road exerts a force to change the car’s direction.
For a ball bouncing from a wall, the wall exerts a force on the ball, causing the ball to change direction.
Motion
Introduction Section 0 Lecture 1 Slide 20
Lecture 3 Slide 20
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Why Velocity Is So Useful
Velocity is a vector and represents a bodies speed and direction.
• A force must act on a body to change its velocity (i.e. its speed, direction or both).
• The force causes the body to accelerate resulting in a change in its velocity.
• Acceleration is a vector and represents the rate of change of velocity with time.
Motion
Introduction Section 0 Lecture 1 Slide 21
Lecture 3 Slide 21
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Acceleration
Motion
Introduction Section 0 Lecture 1 Slide 22
Lecture 3 Slide 22
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Acceleration
Acceleration is the rate at which velocity changes.– Our bodies don’t feel velocity, if the velocity is constant.– Our bodies feel acceleration.
• A car changing speed or direction.• An elevator speeding up or slowing down.
Acceleration can be either a change in the object’s speed or direction of motion.
t1VV
intervalTime velocityinChange
accelerationAverage 2
2smtVa
Motion
Introduction Section 0 Lecture 1 Slide 23
Lecture 3 Slide 23
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Instantaneous Acceleration
Instantaneous acceleration is the acceleration at that precise instant in time.
It is the rate at which velocity is changing at a given instant in time.It is found by calculating the average speed, over a short enough time that the speed does not change much.
Motion
Introduction Section 0 Lecture 1 Slide 24
Lecture 3 Slide 24
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Acceleration: Vector Direction
The direction of acceleration vector is given by the direction of the change in the velocity vector, .
- Acceleration vector in same direction as velocity when velocity is increasing.
- When the velocity is decreasing the change in is in the opposite direction to motion (ie. to slow car down)
- Acceleration vector is opposite direction when velocity is decreasing.- Deceleration is negative acceleration.
1V 2V
1V V+ =
2V
acar
accelerating
V
1V 2V
+ =car
decelerating
1V V 2V
a
V
Motion
Introduction Section 0 Lecture 1 Slide 25
Lecture 3 Slide 25
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Example: Negative Acceleration
Jet preparing to land
Initial velocity V1=200 km/hr (=55.6 m/s)
Final velocity V2=120 km/hr (=33.3 m/s)
Time interval t=5 sec
sma2/
56.553.33
tVV
tV
a12
In general:- Whenever the velocity is changing we say the object is accelerating (positive or negative).
Acceleration:
runwaytowarda 46.4 sm 2/
Motion
Introduction Section 0 Lecture 1 Slide 26
Lecture 3 Slide 26
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Return to car on a bendCar moved at a constant speed but its direction continuously
changed – thus its velocity was changing.
• But we now know that velocity changes are produced by an acceleration.
• Thus when the car rounds the bend at a constant speed it is accelerating!!• Direction of acceleration is given by direction.
Question: what is ?
Result: the vector acts towards the center of curvature of the bend!
V
V
AccelerationDirection
1V
2V
2V
1V
V+ =1V V
2V
V
Motion
Introduction Section 0 Lecture 1 Slide 27
Lecture 3 Slide 27
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
This is why the car does NOT change speed but you still feel a force on your body as you round the bend… (change in direction).
Thus the acceleration is also directed towards the center of curvature.
• Force is due to friction of tires on road enabling the car to change direction.
For a given speed the acceleration experienced (force) depends on the curvature of the bend.
Skiing - sudden turns create large accelerations & large associated forces!
Example:
sharp shallow
2V
2V 2V 1V1V
1V1V
2VLarge
t
Va Small
t
Va
V V
Motion
Introduction Section 0 Lecture 1 Slide 28
Lecture 3 Slide 28
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Graphing Motion
Motion
Introduction Section 0 Lecture 1 Slide 29
Lecture 3 Slide 29
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Graphing Motion
Time
Dis
tanc
e
Time
Spe
ed
Time
Acc
eler
atio
n
Objectives: Understand what position, speed and acceleration are Learn to graph them versus time Develop some intuition for common situations
Consider: Standing still Constant speed (different magnitudes) Constant acceleration (different magnitudes) Constant deceleration (different magnitudes) Arbitrary motion
Motion
Introduction Section 0 Lecture 1 Slide 30
Lecture 3 Slide 30
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Standing Still
Time
Dis
tanc
e
Time
Spe
ed
Time
Acc
eler
atio
n
Motion
Introduction Section 0 Lecture 1 Slide 31
Lecture 3 Slide 31
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Constant Speed
Time
Dis
tanc
e
Time
Spe
ed
Time
Acc
eler
atio
n
Motion
Introduction Section 0 Lecture 1 Slide 32
Lecture 3 Slide 32
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Constant Speeds
Time
Dis
tanc
e
Time
Spe
ed
Time
Acc
eler
atio
n
Motion
Introduction Section 0 Lecture 1 Slide 33
Lecture 3 Slide 33
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Constant Acceleration
Time
Dis
tanc
e
Time
Spe
ed
Time
Acc
eler
atio
n
Motion
Introduction Section 0 Lecture 1 Slide 39
Lecture 3 Slide 39
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 3
Motion
Vectors: Velocity and Acceleration
Motion
Introduction Section 0 Lecture 1 Slide 40
Lecture 3 Slide 40
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Scalars and VectorsScalar: Measure of quantity or size
Sometimes called “magnitude”.Examples: Length, volume, mass, temperature, speed…
Vectors: Many measurements in physics require a knowledge of the magnitude and direction of quantity. These are termed vector quantities.Examples: Velocity, acceleration, force, electric field…
Direction is an essential feature of a vector quantity.Example: Flying at 1000 km/hr due North is quite different to the same speed due East!
Vectors require 2 pieces of information MAGNITUDE and DIRECTION.
Motion
Introduction Section 0 Lecture 1 Slide 44
Lecture 3 Slide 44
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
Next Lab/Demo: Free Fall
Tuesday 1:30-2:45 ESLC 53
Ch 2
Next Class: Wednesday 10:30-11:20
BUS 318 roomReview Ch 3
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