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

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.

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

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

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.

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