Distance Time and Speed KS 3 Revision Boardworks

Distance, Time and Speed KS 3 Revision © Boardworks Ltd 2003

Distance, Time and Speed To work out the speed of an object you need to know: • the distance traveled • how long it took to travel that distance © Boardworks Ltd 2003

Formula triangle Use this equation: distance SPEED = time Formula triangle d s x t Speed is measured in many 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. © Boardworks Ltd 2003

Formula triangle © Boardworks Ltd 2003

Examples A boy travels from his home to the cinema, a distance of 10 km in 1 hour. Calculate his speed in km/h. Speed in km/h = d s x t = d (distance in km) t (time in h) 10 km 1 h = 10 km/h Cover the quantity you want to calculate - s (speed) © Boardworks Ltd 2003

You sometimes have to change the units in this type of problem - here is the same problem again A boy travels from his home to the cinema, a distance of 10 km in 1 hour. Calculate his speed in m/s. (1 km = 1000 m) d (distance in m) Speed in m/s = d s x t Cover the quantity you want to calculate - s (speed) t (time in s) = 10, 000 m 3600 s 1 x 60 = 2. 8 m/s Click for solution © Boardworks Ltd 2003

Questions 1. A group set off from home and walk at an average speed of 3. 6 km/h. How far would they travel in 2 hours? Give your answer in km. Click for solution d s x t Distance (km) = Speed (km/h) x time (h) = 3. 6 km/h x 2 h = 7. 2 km © Boardworks Ltd 2003

2. How long would it take a woman to walk 10 km if her average speed is 5. 4 km/h ? Click for solution Time = d Time = s x t distance speed 10 km 5. 4 km/h Time = 1. 85 hours © Boardworks Ltd 2003