The document explains how to interpret speed-time graphs, identifying motion states such as rest, constant speed, and changing speed. It discusses the calculation of acceleration from the graph's gradient and the determination of distance traveled from the area under the graph. Additionally, it covers concepts of linear motion, constant acceleration, and deceleration, emphasizing the relationship between acceleration, speed changes, and free fall near Earth.

1. MOTION
SPEED-TIME GRAPH

2.  Plot and interpret a speed–time graph
 Recognise from the shape of a speed–time
graph when a body is
– at rest
– moving with constant speed
– moving with changing speed
 Calculate acceleration from the gradient of a
speed–time graph
 Calculate the area under a speed–time graph
to work out the distance travelled for motion
with constant acceleration
OUTCOME

3.  Recognise linear motion for which the
acceleration is constant
 Recognise motion for which the acceleration is
not constant
 Understand deceleration as a negative acceleration
 Demonstrate understanding that acceleration and
deceleration are related to changing speed
including qualitative analysis of the gradient of a
speed–time graph
 State that the acceleration of free fall for a body
near to the Earth is constant
OUTCOME

4.  Straight horizontal line along
x-axis
 Stationary body
 Speed = 0
Object moving at rest

6.  Straight horizontal line
 Acceleration = zero
Object moving with constant speed

7.  Linear motion is motion across a
straight line.
 Acceleration on a speed-time
graph is constant when the line is
straight.
 Straight line passing through origin
Object moving at a constant acceleration

8.  Line curving downwards
indicating decreasing
acceleration (A)
 Line curving upwards
indicating increasing
acceleration (B)
Object moving at a varying speed
A
B
If on the speed-time graph the line is bent or curved it does
not have a constant acceleration, because the gradient of the
line changes.

9. Speed – time graph

10.  Graph of speed of a body against time.
◦ Speed plotted along Y axis
◦ Time plotted along X axis
 Gradient of speed-time graph = acceleration
m = a
Speed-time (v-t) graph
Acceleration, a =

11. Speed – time graph
• With this graph we can tell three things;
• the speed; directly off of the graph.
• the acceleration; by calculating the gradient of the
line.
• the distance it has travelled; by calculating the area
under the graph.

12. Speed – time graph
Speed = 16 m/s

13. Gradient, m
Gradient is a unit less quantity
Gradient, m = =
= 170 – 10 / 32 – 4 = 5.7

14. Calculating Gradient, m
 Gradient of speed-time graph = acceleration
 m = a =
= 40 – 10 / 4 – 1
= 10 m/s2
m =
m =
= 40 – 10 / 4 – 1
m = 10
a = 10 m/s2
m = a

15. Distance travelled from Speed – time graph
• Area under speed-time graph = distance travelled (s)
s = A
= (½ × b × h) + (l × b) + (½ × b × h)
= (½ × 10 × 16) + (10 × 16) + (½ × 5 × 16)
= 80 + 160 + 40
= 280 m
A B C

16. Speed – time graph
• Area under speed-time graph = distance travelled s)
s = Area of trapezium
= ½ × (base1 + base2) × h
= ½ × (10 + 25) × 16
= 280 m
A B C
base1
base2

17. Demonstrate a qualitative understanding that
acceleration is related to changing speed.
• Acceleration is the rate of which an object
changes speed, so when a speed changes, we
assume that the acceleration has either increased
or decreased.
Acceleration, a =
• Deceleration refers to acceleration in the direction
opposite to the direction of the velocity

18. State that the acceleration of free fall for a body
near to the Earth is constant
• Acceleration is the rate of which an object
changes speed, so when a speed changes, we
assume that the acceleration has either increased
or decreased.