10 On Friday, Molly cycles from her house to the gym. The travel graph shows her journey. Molly stays at the gym for 50 minutes. She then cycles back to her house at 24 km/h. a Copy and complete the travel graph. b What time does Molly leave home? c How far is the gym from Molly’s house? 11 Distance (km) Unit 9 Graphs 14 12 10 8 6 4 2 0 1100 1200 1300 1400 Time 1500 Exam-style question Distance from Junction 12 (kilometres) Debbie drove from Junction 12 to Junction 13 on a motorway. 40 30 Exam hint You could plot Ian’s journey on the graph to compare the speeds. Or, you could work out Debbie’s speed from the graph. 20 10 0 0 10 20 30 Time (minutes) The travel graph shows Debbie’s journey. Ian also drove from Junction 12 to Junction 13 on the same motorway. He drove at an average speed of 66 km/hour. Who had the faster average speed, Debbie or Ian? You must explain your answer. (4 marks) June 2013, Q11, 1MA0/1H Key point 8 A rate of change graph shows how a quantity changes over time. On a velocity–time graph the gradient represents the acceleration. i ii iii iv Time (seconds) d Time (seconds) Starts from rest and velocity steadily increases. Travels at a steady velocity. Starts from 5 m/s and steadily increases in speed. Starts from 8 m/s and velocity steadily decreases. Velocity (m/s) Time (seconds) c Velocity (m/s) b Velocity (m/s) a Velocity (m/s) 12 Match each velocity–time graph to one of the sentences. Time (seconds) Q12 communication hint Velocity means speed in a particular direction. 261