Distance-time graph Rola Kombarji Objectives • To be able to draw and plot on a graph. • To be able to describe how distance – time graph tell a story. What is a distance – time graph? • Distance: it is the total length travelled by an object. • International Unit (IU) for distance is meter (m). Distance – time graph • It is a way to visually express motion. It shows how far an object has travelled at a given time. • X-axis: independent variable, the variable that you are changing. • Y-axis : dependent variable, the variable you are measuring. • Label X-axis and Y-axis • Always write the units • Give your graph a title • Draw line of best fit Distance – time graph Example What do you notice is happening to the distance every 2 seconds? Speed • The gradient or the slope of the line on the graph tells us the speed or how fast the object is moving. • The steeper the slope the faster the object is moving. How to calculate the speed? Example What do you conclude? Constant speed V.S changing speed Conclusion Solve the following • How far did the car travel in the first 4 sec? • What was the speed of the car in the first 4 sec? • How long was the car stationary? Book p: 85 d Answer • 1- section E, it is steeper, Rana moved a greater distance in a shorter time. • 2a- Amira • B- David ( as time changed from 15 to 20 minutes the distance did not change) . • C- David was the slowest at the start. • D- amira was the slowest at the end since she covered the shortest distance in 5 minutes. • E- average speed= total distance/ total time • Total distance of amira = 4500 m. • Total time = 15 min Workbook p : 41 • 1aDistance = 20m , time= 4 sec speed= distance / time = 20m /4sec= 5 m/s. Distance=18 m, time 6.2 sec, speed= distance/time = 18/6.2= 2.9 m/s. Distance= 16m, time= 8 s, speed= distance/time= 16/8.2 = 1.95 m/s B- graph A, since the line is steeper which means the same distance is travelled in less time. WORKBOOK P: 41 • 1A- distance 20m, time= 4 s speed=?? Speed= distance/time 20/4= 5 m/s Distance= 18m , time= 6 s, speed= distance/ time Distance= 16m, time= 8 s, speed= distance/time = 16m/8s= 2 m/s B- graph A, shows the fastest speed since the line is steeper (it crossed the same distance with less time) • 2a-total distance= 600m • 2b- total time= 180 s • 2c- average speed =??? Average speed= total distance/ total time = 600m /180 s= 3.33 m/s • 2- a- 600m • B- 180 s • C- average speed=??? Distance = 600m, time= 180 s Average speed= total distance/ total time Average speed= 600m/180 s = 3.33 m/s Extension: A- 20 m B- the graph gets steeper indicating that the speed is increasing. C- draw line below the existing line D- The larger stone will experience more air resistance, so it speeds up less quickly than the small stone.