provides an overview of the topic of motion in physics teaches students about the idea of velocity and acceleration Explains the idea of gradient and goes in-depth into interpretation of distance-time and velocity-time graphs Provides exercises to test the understanding of students

1. VELOCITY AND ACCELERATION
Actually everything in the world is either at rest or moving
For a moving object, you can characterise its movement by
1) how fast it is going
2) thedirection it is heading towards
The word velocity actually includes tells you both how fast an object is going, as well as its
direction.
This is important, because in the absence of friction or other type of forces, Newton theorised
that an object will travel in a straight line (in other words, same direction) and at a constant
speed.
What this means is that so long as either
1) an object slows down or speeds up
2) an object’s direction of motion changes
Then there is a change of velocity.
Newton theorised that a change of velocity can only be caused by applying a force on an
object.
He also felt that objects with more mass have more inertia. The more the inertia, the more
difficult it is to change its motion.
An oil tanker is a great example of inertia at work!Since an oil tanker doesn’t not have brakes,
it has to set its propeller to propel the ship backwards. There is a change in velocity there, and
the tanker’s large mass allow it to resist the change in motion such that it takes a tanker 10km
before it can grind to a halt.
The formula F = ma relates this idea. a refers to acceleration which refers to any change in
velocity. a is affected by mass… the larger the mass, the smaller the change in velocity!
Graphs can help us understand information easily and is often used to represent velocity and
distances over a time period. In a sense, a graph is like a storybook, telling you a story of
what happens from the start till the end.
From this graph, it tells a quite boring story
that the person or object repeated what he
was doing for 240 seconds
As the distance covered by the guy increased
by 1000m every 40s for 240s, he was clearly
travelling at a constant speed throughout.
You could represent his speed on a speed
time graph that looks like this

2. This story you can see is also the same one, the speed did not change at all for the whole 240
seconds.
Yet the slope of the graph is very useful when we are comparing
one thing against another.
We can precisely measure the relationship between the y-axis
thing and x-axis thing by taking the rise divide by the run.
This tells us that for every unit on the x-axis, how many units
would be reflected on the y-axis
Such as in 10m/s, every second the distance increase by 10m
If A and B represent 2 different cars, which car is travelling
faster? _________
How can we tell which is the faster car?
__________________________________________________
__________________________________________________
Over here in the next graph, what is story that you can see?
The object is at rest and its velocity is 0m/s
For graph (iii), notice that if you try to
measure the gradient, you will find that the
gradient is different and it gets larger as time progresses.
This indicates that the distance per unit time is increasing…
and shows that the velocity is increasing.
For graph (iv), the gradient (rise over run) is constant, this means that
distance per unit time is the same…
And so, the velocity is constant.
To better understand what increasing
velocity got to do with distance travelled, look at how far
away the object on the left is from the starting position as
time goes by.

3. Take after 5s for example, the object travelled 50m or 10m every second, yet it only travelled
2m on the first second, and most of the 50m was travelled in the last 2 minutes…
This is a velocity-time graph. Notice
that velocity is _____________.
Can you calculate the relationship
between velocity and time?
_________________
What will happen in the following
scenario?
The change in velocity is in the same direction as velocity.
Therefore, velocity will increase.
The change in velocity is in the opposite
direction as velocity.
Therefore, velocity will decrease
1a) A bus travels at a constant velocity forward of 12m/s for 5
hours, how would you plot velocity versus time in a graph?
1b) Acceleration of 4m/s2 means that the speed of an object will change by 4m/s every s!
1c) What is the final speed of the bus above if it accelerates forward at 4m/s2 for 20 seconds?
1d) What is the final speed of the bus above if the driver steps on the brake and the bus slow
down by at 4m/s2 for 2 seconds?
2) If a car start moving from rest and accelerated at 3.5m/s2 for 10 seconds, what is its
velocity after 10 seconds?

4. 3) A Cheetah was jogging at 7m/s when it saw a nice prey walking around the area and
started giving chase. The Cheetah reached a top speed of 70m/s in 9 seconds. What is its
acceleration?
Speed-time graph
Between time 0s to 4s, the person is
travelling at
________________________
Between time 4s to 9s, the person is
travelling at
__________________________
Notice that the formula for speed
So distance travelled = speed x time taken
Therefore, the distance travelled by the person in the diagram above is also the area under the
graph.
4) Find the distance travelled by the person between 0s to 9s
5) Sketch the distance time graph for the distance travelled for the moving object represented
by the graph

5. Between time 0s to 4s, the velocity of the runner is ______________
This means that ____________________ must be occurring at _______m/s2
Between time 4s to 8s, the velocity of the runner is _______________
This means that there is no __________________________ because there is
____________________________________________
From 8s to 10s, the velocity of the runner _____________. This means that
_____________________ must be occurring at m/s2
Sketch the distance time graph for the runner.
F = MA