Kinematics

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• Mauritius Institute of Education
• Physics data logging Project

• Kinematics

Dr Y Ramma Mr M Cyparsade Dr F Narod Mr S
Moothoosawmy
2

• Kinematics

• At the end of this lesson you should be able to
• Demonstrate understanding of displacement, speed,
  velocity, average velocity and acceleration,
• Derive the equations of kinematics,
• Represent motion graphically.

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• Kinematics

What do you understand by kinematics?
It is the study of motion of bodies excluding
forces.
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• Kinematics

Displacement
Distance covered in a specified direction. Is it
a scalar or a vector quantity? Justify your
answer.
Port Louis
Flacq
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• Kinematics

Stretch Your Mind
Distance Displacement

• A body moves 10 km in a northerly direction and
  then changes direction to the east and moves for
  20 km.
• What is the distance travelled?
• What is its displacement?

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• Kinematics

Speed
It is the rate of change of distance.
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• Kinematics

Uniform velocity
An object is moving with uniform velocity if it
covers equal displacement in equal time.
10 m
20 m
30 m
40 m
50 m
60 m
70 m
80 m
90 m
100 m
110 m
5 s
10 s
15 s
20 s
25 s
30 s
35 s
40 s
45 s
50 s
55 s
Is the trolley moving with uniform
velocity? Justify your answer.
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• Kinematics

Instantaneous velocity
It is the change of displacement at a particular
instant of time.
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• Kinematics

Average velocity
It is the rate of change of total displacement.
Stretch Your Mind
Calculate the average velocity of an object
starting with initial velocity u and attaining
velocity v during time t.
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10

• Kinematics

Instantaneous and average velocities
What is the average velocity? What is the
instantaneous velocity?
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• Kinematics

Acceleration
It is the rate of change of velocity.
An object starts with initial velocity u, attains
velocity v during time t. calculate the
acceleration of the object.
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• Kinematics

Mathematical Interpretation of Motion
Refer to worksheet 1
In deriving the equations of kinematics, there
are two assumptions that you should take into
consideration. What are they?
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Graphical Representation of Motion

• distance time graph

By looking at the data in the table, can you
deduce the type of motion?
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Graphical Representation of Motion

• Why do we need to represent motion on graph?
• visual interpretation of motion.
• trends can easily be detected.

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Graphs
The axes should be well labelled physical
quantity/unit. There should be a title to the
graph, for e.g. Graph of distance/m against
time/s.

s/m
t/s
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Graphs
The curve/line should occupy maximum space on the
graph.

s/m
The space occupied should be more than 60 of the
total space on the graph.
t/s
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Graphs
The curve/line should not cross the blank space
of the graph paper.

s/m
?
t/s
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Graphs
The curve/line should not exceed any of the axes.
?
s/m
t/s
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Graphs
A line of best fit should be drawn in between
the points.
s/m
x
x
x
x
x
x
t/s
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Graphs
The gradient is determined from the hypotenuse
whose length is greater than half the length of
the line of best fit.
s/m
x
x
x
x
x
x
t/s
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Graphical Representation of Motion

• distance time graph

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Graphical Representation of Motion

• distance time graph

s/m
25
t/s
5
10
15
20
25
30
35
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Graphical Representation of Motion

• distance time graph

s/m
t/s
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Graphical Representation of Motion

• distance time graph

Summary When reading a graph, it is
necessary to pay attention to the physical
quantities on the axes. pay attention to the
units (the exact meaning of the physical
quantities can be deduced from the units). take
note of the changes of the quantity on the y axis
with respect to the x axis.
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Graphical Representation of Motion

• distance time graph
• Stretch Your Mind

With reference to your mathematics knowledge,
how can it be deduced that the object is at rest?
s/m
t/s
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Graphical Representation of Motion

• distance time graph

t/s
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Graphical Representation of Motion
Activity Analysing change of
displacement with time. Motion down an inclined
plane.
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• Mauritius Institute of Education
• Physics data logging Project

• Kinematics

Dr Y Ramma Mr M Cyparsade Dr F Narod Mr S
Moothoosamy
The Mauritius Institute of Education
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Graphical Representation of Motion

• distance time graph

s/m
Explain in full details the type of motion
represented by the two lines.
t/s
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Graphical Representation of Motion

• distance time graph

Explain in full details the type of motion
represented by the two lines.
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Graphical Representation of Motion

• displacement time graph

learn_at_Your Own Pace
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Graphical Representation of Motion

• speed time graph

v/
Explain in full details the type of motion
represented by the graph. Justify your arguments
using your mathematics knowledge.
t/s
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Graphical Representation of Motion

• speed time graph

v/
Explain the type of motion represented by the
graph. Justify your arguments using your
mathematics knowledge.
t/s
Worksheet 2
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Graphical Representation of Motion

• speed time graph

Explain the type of motion represented by the
graph. Justify your arguments using your
mathematics knowledge.
v/
t/s
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Graphical Representation of Motion
Study the velocitytime graph shown below. It
represents the motion of a child walking along a
straight road. Write a description of the childs
motion, including as much detail as you can.
Physics for AQA coordinated Teacher and
Technician Resource Pack CD-ROM
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Graphical Representation of Motion

• Distance time graph
• Uniformly accelerated motion

Explain the type of motion represented by the
graph. Refer to your maths knowledge. With
reference to the graph, can you deduce whether
acceleration is constant?
s/m
264
200
144
96
56
24
t/s
2
4
6
8
10
12
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uniformly accelerated motion

• Uniformly accelerated motion
• The motion of an object is described by the
  equation
• Taking u 10 , a 2 ,
  Interpret the motion on the graph paper.

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uniformly accelerated motion
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acceleration of free fall
Any object when released from a certain height
above ground level will fall with constant
acceleration acceleration of free fall.
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acceleration of free fall
a
t
1
h
t
2
activity
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acceleration of free fall
Stretch Your Mind
m
M
The above two cubes are released from a certain
height. Will they fall with the same acceleration
(assume resistive force is negligible) ? Justify
your answer.
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motion in uniform gravitational field with air
resistance
f
f
upward motion
downward motion
mg
mg
Activity worksheet3-kinematics
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