linear motion
Download
Skip this Video
Download Presentation
LINEAR MOTION

Loading in 2 Seconds...

play fullscreen
1 / 62

LINEAR MOTION - PowerPoint PPT Presentation


  • 204 Views
  • Uploaded on

LINEAR MOTION. Chapter 2. Motion . Everywhere – people, cars, stars, cells, electricity, electrons Rate = Quantity/time How fast something happens. Linear Motion. Motion on a straight path Scalar- Distance and speed Vector – Displacement and velocity. Motion is Relative.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' LINEAR MOTION' - fauna


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
linear motion

LINEAR MOTION

Chapter 2

motion
Motion
  • Everywhere – people, cars, stars, cells, electricity, electrons
  • Rate = Quantity/time
    • How fast something happens
linear motion1
Linear Motion
  • Motion on a straight path
    • Scalar- Distance and speed
    • Vector – Displacement and velocity
motion is relative
Motion is Relative
  • Everything moves
    • Things that seem at rest are moving in relation to stars and sun
      • Book on a desk moves at 30 km/sec in relation to the sun
      • Same book is even faster in the galaxy
  • In this chapter – we look at motion compared to earth
speeds
Speeds
  • Snail - 2 meters/day
  • Indy racecar – 300 km/hr
  • Space shuttle – 8 km/sec
speed
Speed
  • Distance / time
    • “per” – divided by – “/”
  • Any combination of units is useful depending on situation
    • Km/hr, cm/day, light-years/hour
  • Most common – m/sec and mile/hr
average speed
Average Speed
  • Total distance/time interval
  • Examples:
    • 60 km in 1 hour = 60 km/hr
    • 240 km in 4 hour = 60 km/hr
      • Note the units
  • Does not indicate all the stops and starts
constant speed
Constant Speed
  • If the speed does not change over a long period, it is like Average speed
  • Length = velocity x time
  • l = vcont
instantaneous speed
Instantaneous Speed
  • Speed at any moment
  • Speed can vary with time
  • Speedometer – measures instantaneous speed
chapter assessment questions

Chapter

Chapter Assessment Questions

2

Question 2

Refer the adjoining figure and calculate the distance between the two signals?

  • Insert graph
  • 3 m
  • 8 m
  • 5 m
  • 5 cm
chapter assessment questions1

Chapter

2

Chapter Assessment Questions

Answer 2

Answer:C

Reason:Distance d = df – di

Here, df = 8 m and di = 3 m

Therefore, d = 8 m  3 m = 5 m

questions
Questions
  • The speedometer in every car also has an odometer that records distance:
    • If the odometer reads zero at the beginning of the trip and 35 km a half-hour later, what is the average speed?
    • Would it be possible to attain this average speed and never exceed 70 km/hr?
  • If a cheetah can maintain a constant speed of 25 m/s, it will cover 25 meters every second. At this rate, how far will it travel in 10 seconds? In one minute?
graph of constant speed
Graph of Constant speed
  • Average speed is the slope of the line during an interval
  • If it is a curve, the instantaneous speed is the line tangent to the curve at that point
delta notation
Delta Notation
  • Δ – Greek capital letter – Delta
  • Signifies a change in a quantity

Δl = l f – l i

Δt = t f -t i

v = Δl = l f – l i

Δt t f - t i

velocity
Velocity
  • EDL (every day life) – speed and velocity are interchangeable
  • Physics – Velocity – speed in a direction
    • 60 km/hr North
  • Question – The speedometer of a car moving northward reads 60 km/hr. It passes another car that travels southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity?
constant velocity
Constant Velocity
  • Constant speed and direction
  • Must move in a straight line
    • Curves change the direction
  • Changing velocity- in a car there are 3 things to change velocity –
    • Gas
    • Brakes
    • Steering wheel
the displacement vector
The Displacement Vector
  • Displacement is the straight-line shift in position from Poto Pf
    • Included length and direction
  • Vector
    • Magnitude
    • Direction
resultant
Resultant
  • The vector that is drawn between two points

Resultant

vector algebra
Vector Algebra
  • Rules for dealing with vectors
  • Helps us understand how to manipulate them
tip to tail method
Tip-to-Tail Method
  • Add vectors by placing tip of one to the tail of the other.
    • The resultant is from the tail of one to the tip of another

A

B

B

A

Resultant

tip to tail method1
Tip-to-Tail Method
  • Order of addition is irrelevant

B

A

A

B

B

A

parallelogram method
Parallelogram Method
  • Use 2 set vectors to make a parallelogram
  • The diagonal is the resultant
multiple vectors
Multiple Vectors
  • Add more than 2 vectors by the tip-to-tail method

Resultant

Resultant

parallel vectors
Parallel Vectors
  • Parallel – Simple sum
  • Anti-parallel (opposite directions) - Difference

Resultant

Resultant

acceleration
Acceleration
  • How fast is velocity changing
  • Acceleration is a RATE (of a rate)
  • Change in velocity
    • Acceleration
    • Deceleration
    • Change in direction
  • Acceleration = Change in velocity/time
question
Question
  • Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then 45 to 50 km/h. What is its acceleration?
  • In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle?
average acceleration
Average Acceleration

a – acceleration (m/s^2)

v – velocity (m/s)

t – time (s)

average acceleration problem
Average acceleration problem

Problem – What is the acceleration of a car the screeches to a stop from 96.54 km/h in 3.7 seconds?

instantaneous acceleration
Instantaneous Acceleration
  • Velocity vs. Time graph
    • Slope of line tangent is equal to ACCELERATION
    • Sign of Slope
      • Positive – accelerating
      • Negative - decelerating
velocity time graph of accelerating car
Velocity-Time Graph of Accelerating Car

Tangent

Slope = acceleration

velocity

time

uniform accelerated motion
Uniform accelerated motion
  • In the real world, acceleration is seldom constant
  • In problems, we can consider it constant for a few moments
  • Motion is in a straight line
    • Vf – final velocity
    • Vi – initial velocity
uniform accelerated motion1
Uniform accelerated motion
  • vf = vi + at
  • Problem – What is the final speed of a bicyclist moving at 25.0 km/h who accelerates +3.00 m/s^2 for 3.00 sec?
the mean speed
The Mean Speed
  • What is vav for an object that is uniformly accelerating from vi to vf?

Mean speed = vav = ½ (vi + vf)

area under the graph
Area under the Graph
  • Equals the total distance moved

Area of a retangle = m/s x s = Meters

more complex
More complex
  • Area under still equals distance
mean speed theorem
Mean Speed Theorem

s = ½ (vi + vf) t

Problem- A bullet is fired with a muzzle speed of 330m/s down a 15.2 cm barrel. How long does it take to travel down the barrel?

constant acceleration equations the big five
Constant Acceleration Equations THE BIG FIVE
  • vf = vi + at
  • vav = ½ (vi + vf)
  • s = ½ (vi + vf) t
  • s = vit + ½ at²
  • vf² = vi² + 2as
when v f is unknown
When vf is unknown
  • One sports car can travel 100.0 ft in 3.30 seconds from 0m/s. What is the acceleration?
when t is unknown
When t is unknown

Problem – What is the cheetah’s acceleration if it goes 0 to 72 km/hr in 2.0 seconds?

- How far will it go to be moving 17.9 m/s?

freefall how fast
Freefall – How Fast
  • An apple gains speed as it falls
  • Gravity causes acceleration
  • EDL – air resistance effects freefall acceleration
freefall
Freefall

Elapsed Time Instant. Speed (m/sec)

0 0

1 10

2 20

3 30

4 40

t 10t

freefall1
Freefall
  • Acceleration = change in speed

time

= 10 m/s/s = m/s2

Unit – meter/second/second

speed time interval

  • Equations : a = V instantaneous /t

V instantaneous = at

gravity acceleration
Gravity acceleration
  • g = acceleration due to gravity
    • Actually measures 9.81 m/s2
    • In English – 32 ft/sec²
  • Speedinstantaneous = acceleration x time

vinstantaneous = gt

question1
Question
  • What would the speedometer reading on the falling rock be 4.5 seconds after it drops from rest?
  • How about 8 seconds after it is dropped?
  • 15 seconds?
what about an object thrown upward
What about an object thrown upward?
  • On the way up it decelerates 9.81m/s2
  • On the way down it accelerates 9.81m/s2
free fall how far
Free Fall – How Far?
  • Fast and far are different
  • At the end of 1 sec the speed is 9.81m/s2
    • Did it travel 9.81 m?
      • NO – it was accelerating from 0 m/s
    • 0 m/s  9.81 m/s
      • Average speed = 4.90 m/s
question2
Question
  • During the span of fall, the rock begins at 10 m/s and ends at 20 m/s. What is the average speed during this 1-second interval. What is its acceleration?
distance in gravity
Distance in gravity
  • Mathematical pattern for the distance something falls in time:

distance = ½ gravity x time2

d= ½ gt2

questions1
Questions
  • An apple falls from a tree and hits the ground in one second.
    • What is the speed upon striking the ground?
    • What is its average speed during the one second?
    • How high about ground was the apple when it first dropped?
graphs of motion
Graphs of Motion
  • Velocity vs. Time- freefall

Linear - directly proportional

Slope is constant = acceleration

Velocity

Time

graphs of motion1
Graphs of Motion
  • Distance vs. Time

Parabolic

Slope is variable = Speed

Distance

Time

air resistance
Air resistance
  • Effects feathers and paper
  • Not much effect on things with low profiles
how fast far and quickly
How fast, far, and quickly
  • Don’t mix up fast and far
  • Acceleration – rate of a rate
    • Rate at which velocity changes
  • Be patient – it took 2000 years from Aristotle to Galileo to straighten it all out!!
ad