with the following images? Connect What links can you make with the following images?

KS3 Physics Speeding Up

Speeding Up Distance, time and speed

Outcomes Learning L.O.: Interpret distance-time graphs to describe changes in motion and calculate average speed. Must: give some unit of speed, distance and time. Should: be able to calculate speed using s=d/t. Why: interpret sections of d-t graphs; explaining motion during a period of time.

Distance, time and speed Share new Information 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 Share new Information Calculating average speed Average speed is calculated using this equation: d s x 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 used will give the units to be used for speed.

Speed formula triangle Share new Information

Speed calculation example Share new Information Speed calculation example A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in km/h. d s x t d (distance in km) average speed (in km/h) t (time in h) = 10 km 1 h = = 10 km/h Cover the quantity to be calculated - s (speed)

Speed calculation example – units check Sometimes the units have to be changed in a speed calculation. Here is the same problem but with different units: A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in m/s. d s x t d (distance in m) average speed (in m/s) t (time in s) = 3600 s 10,000 m = 1x60x60 = 2.8 m/s Cover the quantity to be calculated - s (speed) Share new Information

Speed calculation – question 1 A group set off from home and walk at an average speed of 3.6 km/h. How far would they travel in two hours? Give your answer in km. d s x t distance (km) = speed (km/h) x time (h) = 3.6 km/h x 2 h = 7.2 km Share new Information

Speed calculation – question 2 How long would it take a woman to walk 10 km if her average speed is 5.4 km/h ? time = distance speed d s x t 10 km 5.4 km/h = = 1.85 hours Share new Information

Demonstrate Understanding Demonstrate your understanding of using the speed equation. Attempt as many questions as you can from the worksheet.

Review and Reflect Write down the speed equation 3 times. Each time, you need to show how to calculate: Speed Distance Time and Reflect

Car graphing activity – instructions The following graphing experiment shows an animation of a car travelling along a straight road. 1. Copy the results table shown on the next slide and complete it as the movie is played. 2. Record the distance the car has travelled every five seconds. 3. Plot a graph of your results.

Car graphing activity – results table layout Results table for distance/time graph Time/seconds Distance/metres 5 10 15 20 25 30 35 40 45 50 55

Car graphing activity – animation

Car graphing activity – results table Results table for distance/time graph Time/seconds Distance/metres 5 16 10 76 15 186 20 234 25 484 30 634 35 784 40 904 45 974 50 994 55

Car graphing activity – results graph

Car graphing activity – results graph

Car graphing activity – results graph analysis The speed of the car is changing – the graph is not flat. The slope of the graph is less steep as the car begins to slow down. The car has stopped. The graph is flat – the distance of the car from the start point is not changing. The graph is straight – there is no change in speed. The car is going fast but at a constant speed. The graph is straight in this part of the journey. The car is starting to move. The curve shows that the speed is changing. The curve is upwards as the car accelerates at the start of the journey.

Gradient of a distance/time graph The speed of the car can be calculated by looking at the gradient of the distance/time graph. Speed is “Distance Travelled divided by Time Taken” These values can be read off the distance/time graph at different points, and this is the same as the gradient of the graph.

Gradient of a distance/time graph Consider the gradient of this graph at the point shown by the two arrows in a triangle: The car has travelled from 200m to 800m = 600m. It took from 16s to 36s to travel this distance = 20s. So the speed at this point = 600m/20s = 30m/s.

Reflect: Select two numbers between 1-25, write these in the margin of your book. Now complete the sentence/question from the numbers that you have chosen…