Movement and Speed 06 December 2018 Objectives To demonstrate how speed is calculated and measured in a range of situations.

Starter (5 mins) Show the students a video clip of a 100 m race between a sprinter and a cheetah (https://www.youtube.com/watch?v=gzF2_AoPBY4). Before the race begins, ask the students which will finish first and to describe the journey in terms of speed. After the clip, discuss what was shown in terms of average speed and instantaneous speed, linking this to P1.1 and P1.4 in the Student’s Book.

Average speed vs. instantaneous speed The speed of a race car at any point around a track is called the instantaneous speed. A car will have a different instantaneous speed at each of the points around the track. Average speed is the total distance travelled divided by the total time taken. It is never bigger than the instantaneous speed.

Main The students measure the speed of an object in a practical task using either ticker tape, light gates or even a ruler and stopwatch. Different groups try different techniques so they understand the technology available and the precision of different instruments or techniques. Discuss the concepts of precision and error; students can use timers with different resolutions and consider reaction times.

Distance, time and speed To work out the speed of an object you need to know: the distance travelled how long it took to travel that distance.

Calculating average speed Average speed is calculated using this equation: d s t formula triangle total distance total time Average speed = Speed can be measured in different units, e.g. m/s, km/h, km/s, miles per hour. The units of distance and time will determine the units to be used for speed. Speed Worksheet 1 accompanies this slide. It has been designed to be used at any point in the presentation to help to reinforce how speed is calculated. This worksheet involves an outdoor activity.

Words and units

Speed formula triangle

Speed calculation example A girl takes 30 minutes to travel around a cross-country ski course: a distance of 10 km. Calculate her average speed in km/h. 10 km distance (in km) average speed (in km/h) time (in h) = 0.5 h = 10 km 20 km/h

Speed calculation example – units Sometimes the units have to be changed in a speed calculation. Calculate the average speed of the skier in m/s. 10 km average speed (in m/s) time (in s) = distance (in m) 3600 s 10,000 m = 2.8 m/s

Distance calculation A boy sets off for a walk around his village at an average speed of 3.6 km/h. How far will he travel in 30 minutes? Give your answer in km. distance (km) = speed (km/h) × time (h) = 3.6 km/h × 0.5 h = 1.8 km

Time calculation – question 1 How long would it take the boy to walk 200 m to the church, if his average speed was 0.8 m/s? time = distance speed 200 m 0.8 m/s = = 250 seconds

Plenary (10 mins) The different groups of students should critically evaluate the measurement techniques used by all groups and use the results of this discussion to suggest improvements in experiments. Alternatively they can concentrate on vocabulary and try the Literacy Brainteaser ‘Unit 1: Describing movement’.

Codebreaker Work out the key words from these combinations! Example: 54G48 = LIGHT 1. 773E3 2. 34S8262E 3. 22C3537284N4 4. 4R2343N8 5. 347T26C3-846E 47A74 6. 283R24E 773E3

Were you successful? accelerating Average speed distance 34S8262E = DISTANCE 22C3537284N4 = ACCELERATING 4R2343N8 = GRADIENT 347T26C3-846E 47A74 = DISTANCE-TIME GRAPH 6. 283R24E 773E3 = AVERAGE SPEED accelerating Average speed distance distance–time graph gradient light gate Relative time