Year 10 Physics unit looking at acceleration.

1. OBJECTS IN MOTION.
03. Acceleration.
Ian Anderson
Saint Ignatius College Geelong

2. WHAT IS ACCELERATION?
When a car takes off from
the traffic lights it will
increase its speed until it
reaches the speed limit.
Acceleration is described
as the rate at which speed
changes.
The quicker the car
increases its speed, the
greater its acceleration.
Source: Sharwood (2006)

3. CALCULATING ACCELERATION.
Acceleration = the rate of change of speed.
Acceleration =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
=
𝑓𝑖𝑛𝑎𝑙 𝑠𝑝𝑒𝑒𝑑 − 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑠𝑝𝑒𝑒𝑑
𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
𝑎 =
∆𝑠
∆𝑡
𝑎 =
(𝑣 − 𝑢)
𝑡

4. CALCULATING ACCELERATION.
Acceleration is measured in units of
 metres per second per second (m/s/s), or
 metres per second squared (m/s2 or ms-2).
If an object slows it is decelerating. Deceleration is
negative acceleration.
Source:
http://oneinamillionsophie.blogspot.com.au

5. CALCULATING ACCELERATION.
In a 100m sprint, Usain Bolt is
able to reach a speed of 12 m/s in
6 s.
What is his acceleration?
Acceleration =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
=
(𝑣 − 𝑢)
𝑡
v = 12 m/s
u = 0 m/s
t = 6 s
Source:
http://www4.uwsp.edu/physastr/kmenning/Phys203

6. CALCULATING ACCELERATION.
Acceleration =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
=
(𝑣 − 𝑢)
𝑡
v = 12 m/s
u = 0 m/s
t = 6 s
Acceleration =
(12 −0)
6
= 2 m/s2
Source:
http://www4.uwsp.edu/physastr/kmenning/Phys203

7. CALCULATING ACCELERATION.
If the speed of a car changed
from 0 to 60 km/h in 6 s, what
was its acceleration (in km/h/s)?
Acceleration =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
=
(𝑣 − 𝑢)
𝑡
v = 60 km/h
u = 0 km/h
t = 6 s
Source: http://www.lefrelonvert.com/2010/09/elvis-blu-
ray-collection/

8. CALCULATING ACCELERATION.
Acceleration =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
=
(𝑣 − 𝑢)
𝑡
v = 60 km/h
u = 0 km/h
t = 6 s
Acceleration =
(60 − 0)
6
= 10 km/h/s
Source: http://www.lefrelonvert.com/2010/09/elvis-blu-
ray-collection/

9. ACCELERATION AND GRAPHS.
The gradient of a speed-time graph gives you the rate
of acceleration.
 A steep speed-time graph indicates a higher
acceleration than a graph with a lesser slope.
Source: Rickard et al. (2006)

10. ACCELERATION AND GRAPHS.
A car accelerates from rest until it reaches 13 m/s
after 5 s. It then continues at that speed for 45 s
before it approaches a red traffic light. The driver then
slows the car down until it stops at the red light 10 s
later.
Source: Sharwood
(2006)

11. ACCELERATION AND GRAPHS.
What was the car’s acceleration
 in the first 5 s?
 between 5 & 50 s?
 between 50 & 60 s?
Source: Sharwood
(2006)

12. ACCELERATION AND GRAPHS.
 The areas under the graph lines tell us the distance
travelled by the car in each time period.
 The area under the whole graph tells us the
distance between the two traffic lights.
Source: Sharwood
(2006)

13. ACCELERATION AND GRAPHS.
What was the distance covered by the car
 in the first 5 s?
 between 5 & 50 s?
 between 50 & 60 s?
 for the whole 60 s?
Source: Sharwood
(2006)

14. BIBLIOGRAPHY.
Rickard, G., Phillips, G., Ellis, J., Jeffery, F., &
Roberson, P. (2006). Science Dimensions 4:
Coursebook. Melbourne: Pearson Education
Australia.
Sharwood, J. (Ed.). (2006). Science Edge 4.
Melbourne: Thomson Learning.

15. http://SICkScience10.wikispaces.com/