Chapter 2 - Motion in One Dimension - PowerPoint PPT Presentation

1 / 36
About This Presentation
Title:

Chapter 2 - Motion in One Dimension

Description:

Chapter 2 - Motion in One Dimension 2.1 - Displacement and Velocity – PowerPoint PPT presentation

Number of Views:264
Avg rating:3.0/5.0
Slides: 37
Provided by: emel3
Category:

less

Transcript and Presenter's Notes

Title: Chapter 2 - Motion in One Dimension


1
Chapter 2 - Motion in One Dimension
  • 2.1 - Displacement and Velocity

2
Motion
  • One-dimensional motion is the simplest form of
    motion
  • e.g. a train on a straight track (forward or
    backward)
  • In this chapter we will consider only
    one-dimensional motion

3
Motion
  • The first step in analyzing motion is to choose a
    frame of reference.
  • If an object is at rest, its position does not
    change with respect to a frame of reference.
  • When we choose this frame of reference, we need
    to remember to remain consistent.

4
Displacement
  • Displacement is the change in position of an
    object.
  • It is the length of the straight line drawn from
    its initial position to its final position

Displacement change in position final
position - initial position
5
Displacement
  • Displacement is not always equal to the distance
    traveled

6
Displacement
  • Displacement can be positive or negative

7
Average Velocity
  • Knowing the distance traveled or the displacement
    doesnt tell completely describe the motion of an
    object
  • Knowing the speed is important for evaluating
    motion
  • Average velocity is the total displacement
    divided by the time interval during which the
    displacement occurred

8
Average Velocity
  • The Average Velocity can be positive or negative
  • Equal to the constant velocity needed to cover
    the given displacement in a given time interval
  • It is NOT the average of the starting and ending
    velocities
  • Example A car travels from city A to city B (100
    km). If the first half of the distance is driven
    at 50 km/h and the second half is driven at 100
    km/h, what is the average velocity of the car?

9
Practice
  • Page 44, Practice 2A

10
Average Speed
  • Velocity is not the same as speed
  • Velocity has both magnitude AND direction
  • Speed has only a magnitude

11
Graphical Interpretation of Velocity
  • In a position-time graph, we can determine the
    vavg by drawing a straight line between two
    points on the graph

12
Graphical Interpretation of Velocity
13
Instantaneous Velocity
  • The velocity of an object at some instant

14
Chapter 2
  • Section 2.2 - Acceleration

15
Acceleration
  • Most objects in motion dont move with a constant
    velocity
  • Acceleration measures the rate of change in
    velocity in a given time interval

16
Problem
  • Find the acceleration of an amusement park ride
    that falls from rest to a speed of 28m/s in 3.0s.
  • 9.3 m/s2

17
Acceleration
  • Acceleration has both magnitude and direction
  • If an object (i.e. a car) is moving in the
    positive direction and is speeding up, the
    acceleration is positive
  • If an object is moving in the positive direction
    and is slowing down, the acceleration is negative
  • If an object (i.e. a car) is moving in the
    negative direction and is speeding up, the
    acceleration is negative
  • If an object is moving in the negative direction
    and is slowing down, the acceleration is positive

18
Constant acceleration
  • The slope of a velocity-time graph gives the
    acceleration
  • When acceleration is constant, the velocity is
    increased by the same amount during each time
    interval.
  • The displacement for each time interval increases
    by the same amount

19
Displacement
  • Depends on
  • Initial velocity
  • Acceleration
  • Time

When acceleration is constant, Vavg is the
average of Vi and Vf
20
Displacement
  • When acceleration is constant

21
Displacement
  • The area under the curve in a graph of velocity
    versus time equals the displacement during the
    time interval

22
Problem
  • A bicyclist accelerates from 5.0 m/s to a
    velocity of 16 m/s in 8 s. Assuming uniform
    acceleration, what distance does the bicyclist
    travel during this time interval?
  • 84m

23
Final Velocity
  • Depends on
  • Initial velocity
  • Acceleration
  • Time

24
Constant Acceleration
25
Displacement with constant uniform acceleration
26
Final velocity after any displacement
Remember that the square root may be either
positive or negative
27
Problem
  • An aircraft has a landing speed of 302 km/h. The
    landing area of an aircraft carrier is 195 m
    long. What is the minimum uniform acceleration
    required for a safe landing?
  • -18.0 m/s2

28
Summary
29
HW Assignment
  • Page 49, Practice 2B, 1 and 4
  • Page 53, Practice 2C, 3 and 4
  • Page 55, Practice 2D, 2 - 4
  • Page 58, Practice 2E, 2, 5, 6

30
Chapter 2
  • Section 2.3 - Falling Objects

31
Free Fall
  • Motion of an object falling with a constant
    acceleration
  • In the absence of air resistance all objects
    dropped near the surface of a planet fall with
    the same constant acceleration
  • The symbol for free-fall acceleration is g
  • At the surface of the earth, the magnitude of g
    is approximately 9.81 m/s2.

32
Free Fall
  • This acceleration is directed downwards
  • a -g -9.81 m/s2
  • What goes up, must come down
  • Fig 2-15, pg 61
  • Initial velocity of 10.5 m/s, acceleration is
    -9.81 m/s2
  • After 1 s, v 0.69 m/s, acceleration is
    -9.81m/s2
  • After 2 s, v -9.12 m/s (directed downward), a
    9.81 m/s2

33
Free Fall
34
Free Fall
  • FREELY FALLING OBJECTS ALWAYS HAVE THE SAME
    DOWNWARD ACCELERATION

35
Problem
  • A ball is thrown straight up into the air at an
    initial velocity of 25.0 m/s. Create a table
    showing the balls position, velocity, and
    acceleration each second for the first 5.00 s of
    its motion.
  • Find the balls time, position, velocity, and
    acceleration at the top of its flight

36
HW Assignment
  • Pages 72 - 75 34, 38, 40, 41, 46, 50, 56
Write a Comment
User Comments (0)
About PowerShow.com