The questions are on the motion graphs test. Take it under real conditions before reading the mark scheme.
Quick answer: On a distance-time graph the gradient is the speed and a flat line means stopped. This mark scheme gives the model answers and the marks for the 8 questions of the grade 8 science test on motion graphs, from meaning of the gradient to speed and velocity, with the equivalent answers to accept.
The model answers show how to read the graphs and how to calculate. Marks are given for the method as well as for the answer, so check that you showed the gradient or area you used and the correct units.
Level: Grade 8 science (Year 9 · Class 8) · Curriculum: MS-PS2-2
Question 1 Meaning of the gradient (2 marks)
- The speed.
- The acceleration.
Marking: 1 mark each.
Question 2 Mei’s walk (4 marks)
- 30 m.
- 30 ÷ 20 = 1.5 m/s.
- From 20 s to 50 s: 30 s.
- (90 − 30) ÷ 20 = 3.0 m/s.
Marking: 1 mark per part.
Question 3 A lorry journey (4 marks)
- a = 10 ÷ 10 = 1.0 m/s².
- a = 10 ÷ 5 = 2.0 m/s².
- Areas: ½ × 10 × 10 = 50 m; 10 × 20 = 200 m; ½ × 5 × 10 = 25 m. Total = 275 m.
Marking: Part a: 1 mark. Part b: 1 mark. Part c: 1 mark for the method with three areas, 1 mark for 275 m.
Question 4 A cyclist speeds up (2 marks)
a = (v − u) ÷ t = (9.0 − 3.0) ÷ 4.0 = 1.5 m/s².Marking: 1 mark for the formula and substitution, 1 mark for the answer with unit.
Question 5 Describe the graph (2 marks)
- The object moves at constant speed (zero acceleration).
- The object is stationary.
Marking: 1 mark each.
Question 6 Average speed (3 marks)
- 2400 m and 1200 s.
- 2400 ÷ 1200 = 2.0 m/s.
- 2.0 × 3.6 = 7.2 km/h.
Marking: 1 mark per part.
Question 7 Braking (2 marks)
a = (0 − 25) ÷ 5.0 = −5.0 m/s², so a deceleration of 5.0 m/s².Marking: 1 mark for the method, 1 mark for the answer.
Question 8 Speed and velocity (1 mark)
Velocity has a direction as well as a size; speed has size only.Marking: 1 mark for direction.
