1. Speed and Acceleration
CfE Higher Physics
Unit 1
Our Dynamic Universe
Speed and Acceleration
(Revision)

2. Lesson Starter
A skateboarder starting from rest goes down a uniform slope and reaches a speed of 8 m s-1 in 4 s. a) What is the acceleration of the skateboarder? b) Calculate the time taken for the skateboarder to reach a speed of 12 m s-1.
An athlete runs a 1500 metres race in a time of 3 minutes 40 seconds. Calculate his average speed for the race.

3. Average Speed Average speed is the average for the whole journey. m
distance travelled
average speed =
time taken
m/s or ms-1 s
v = t d

4. Instantaneous Speed
Instantaneous speed is the speed at one point in the journey.
To measure instantaneous speed a card is attached to the vehicle and allowed to pass through a light gate connected to an electronic timer.
length of card
instantaneous speed =
time through gate

5. Acceleration Acceleration is the change in speed in unit time.
m/s2 or ms-2 or m/s/s
a = t
v-u
Negative acceleration is deceleration.

6. Speed-Time Graphs speed time OA - constant acceleration AB -
constant speed
BC -
constant deceleration
acceleration =
gradient of graph
distance travelled =
area under graph