Motion- Speed and
Velocity
Speed,Distance and Time
Speed is the the rate at which someone or
something is able to move or operate.
To calculate speed you divide the distance
by time taken.
If the time was measured in seconds (s) and
the distance in meters (meters) the speed
will be written in m/s.
Speed,Distance and Time
A car travels a distance of 300 km in 3
hours. What’s is the car’s speed?
Distance: 300
Time:
3
= 100 km/h
Speed, Distance and Time
But what if this was the question?
A car travels at a speed of 100 km/h for 3 hours,
how far did the car go?
or
How long would it take a car to travel 300 km at a
speed of 100 km/h ?
Speed, Distance and Time
Then we’d have to use the Speed Triangle.
Converting Units
To convert m/s to km/h
Distance covered in 1 sec
=1m
distance covered in
3600s= 3600m
i.e. In 1 hr =3.6km covered
I.e. 1m/s =3.6 km/h
To convert km/h to m/s
Distance covered in 1hr =1km
1hr =3600 seconds
I.e. Distance covered in 3600 sec =
1000 m
Distance covered in 1 sec = 1000/
3600 m
I.e.1 km/hr =0,2777… m/s
1.Convert 10 km/h to m/s
2. Alex drives 30 km for 15 minutes.
What is his speed in km/h?
3. Sally walks 3000 meters in 900
seconds what is her average speed in
km/h
Speed and Velocity
Speed is the the rate at which someone or
something is able to move or operate.
Velocity is the speed of an object or
someone at a certain direction
● For example: Kate walked at a speed of 6
m/s going north she then turned east and
walked at a speed of 6.8 m/s
Acceleration
Acceleration: the rate at which an object
changes its velocity.
Acceleration =
Change in Velocity ➗ Time Taken
Acceleration
A bike starts from rest and
accelerates to 20 m/s over a
period of 6 seconds. What is the
acceleration of the car?
Acceleration
A car’s acceleration is 20 m/s2 it
accelerates for 20 seconds. What is
the change of velocity?
Acceleration
A car decelerates from 20m/s to
60m/s at a rate of 5 m/s2. How long
does this acceleration take the
car?
Distance/Time Graph
Distance/Time Graph
Distance: 10-40 30m
Time: 40-60 20 s
30/20=
1.5 m/s
The slope of a distance
time graph tells us the
speed.
We can tell which
object is going faster
by the graph’s slope,
if objects travelled
the same amount of
distance.
Which one is
faster?
Speed/Time graphs
Constant
Acceleration
Constant
Speed
Constant
Deceleration
Speed/Time Graph
60
50
20/2= 10
Change in Speed:
0-20 --> 20
Time taken: 0-2 2hr
10 k/h2
40
30
20
10
0
1
2
3
4
5
6
Speed/Time graphs
To calculate the
distance you calculate
the area under the graph
60
50
40
30
20
10
0
1
2
3
4
5
6