Chapter 2
Motion in One Dimension
1.
Speed
2.
Displacement
3.
Average and Instantaneous velocity
4.
Acceleration
5.
Motion Diagrams
6.
1D motion with constant acceleration
7.
Law of falling body
1
Dynamics
What is Dynamics?
What is Kinematics?
2
Objects in Motion
How does one describe motion?
3
Position and Displacement
Position
Displacement
Definition
Representation
Units
Definition
Representation
Units
Difference between
displacement and
distance
4
Vector and Scalar
Quantities
What are vectors?
Why do I need them?
How do I represent them
During problem solving on paper
On Diagrams
5
Speed and Velocity
Average Speed
Average Velocity
Definition
Calculation
Units
Definition
Calculation
Units
Difference between speed and velocity
6
Finding Average Velocity on
graphs
7
Instantaneous and Uniform
Velocity
Definition
What is it?
How do I
calculate it
from graph?
What is
uniform
velocity?
8
Example
A toy train moves
slowly along a
straight portion of
track according to
the graph of
position versus
time shown. Find a)
the average
velocity of the total
trip, b) the average
velocity during the
first 4.0s of motion,
c) the
instantaneous
velocity at t=8.0s
9
Acceleration
Definition
Representation
Units
Average acceleration
Instantaneous acceleration
Uniform acceleration
Graphical interpretation
10
Graphical Interpretation
11
Example
A baseball player moves
in a straight-line path
in order to catch a fly
ball bit to the out
field. His velocity as a
function of time is
shown. Find his
instantaneous
acceleration at points
A, B and C.
12
Relationship Between
Acceleration and Velocity
13
Kinematic Equations
Used in situations with uniform
acceleration
v = vo + at
1
(v o + v ) t
2
1
∆x = vot + at 2
2
v 2 = vo2 + 2a∆x
∆x = vt =
14
Example
A bus moving at a speed of 40 m/s
begins to slow at a rate of 3 m/s
each second. Find how far it goes
before stopping?
15
Example
An object starts from rest with
constant acceleration of 10 m/s2
along a straight line. Find a) the
speed at the end of 5 seconds, b)
the average speed at the 5 second
interval, c) the distance traveled in
5 seconds.
16
Graphical Interpretation of
the Equation
17
Galileo Galilee
1564 - 1642
Galileo formulated
the laws that govern
the motion of objects
in free fall
Also looked at:
Inclined planes
Relative motion
Thermometers
Pendulum
18
Free Fall
What is the Law of falling body?
Galileo's hypothesis
Representation
Value of g for earth
Estimated value
Approximate value
Direction of
Why g is not a universal constant?
19
Free Fall – Cases
Thrown Up
Dropped
Thrown down
v=0
vo= 0
vo≠ 0 & -ve
vo≠ 0 & +ve
a = g=-9.8
m/s2
a = g=-9.8
m/s2
a = g=-9.8
m/s2
everywhere
Symmetric or non-symmetric
20
Example
A ball is dropped from rest at a
height of 50 m above the ground,
a) what is the speed just before it
hits the ground? b) how long does
it take to reach the ground? Ignore
air friction
21
Example
Two rocks are thrown vertically up
with a velocity of V and 4V. The
ratio of the maximum heights
reached (ha/hb) by the rocks is…
22
Example
Jack and Jill walk down the hill to
fetch a pail of water. Jack’s
walking path is described by the
equation y=0.1x+5 and Jill’s
walking path is described by the
equation y=0.2x+1. If the source
of water is 13 meters away, who
reached the river first.
23