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Mathematics questions, chapter 9
Nama / NameKelas / ClassTarikh / Date

Speed and Acceleration

40 marks. Use Practice to check each answer as you go, or Exam to answer everything first. You may use a calculator. Show your working for Section B.

Section A: objective questions

12 marks
Choose the correct answer.
1

Question 1

Which statement describes speed?
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A
Speed is a rate: distance divided by time, so it is the distance covered in each unit of time. The time taken for one unit of distance is the inverse of speed, and the total distance of a journey is not a rate at all.
For the teacher: Remembering, low difficulty, standard 9.1.1
Textbook p. 170
2

Question 2

A sprinter runs 100 m in 12.5 s. What is her speed?
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C
Speed = 100 ÷ 12.5 = 8 m/s. 12.5 m/s is just the time, 0.125 m/s divides the other way round (12.5 ÷ 100), and 1 250 multiplies.
For the teacher: Applying, low difficulty, standard 9.1.1
Textbook p. 171
3

Question 3

The table shows the distance of a toy car from its starting point.
Time (s)01234
Distance (m)0481216
Which statement is correct?
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B
Equal distances (4 m) are covered in equal intervals of time (1 s), which is uniform speed. A growing distance alone does not make the speed non-uniform.
For the teacher: Understanding, low difficulty, standard 9.1.2
Textbook p. 172
4

Question 4

The speed of a motorcycle is 72 km/h. What is this speed in m/s?
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D
72 km/h = 72 × 1 000 ÷ 3 600 = 20 m/s (or 72 ÷ 3.6). 259.2 multiplies by 3.6 instead of dividing, and 1.2 is 72 ÷ 60 (km/min).
For the teacher: Applying, low difficulty, standard 9.1.3
Textbook p. 175
5

Question 5

A car travels 90 km in the first 1.5 hours and then 120 km in the next 2.5 hours. What is its average speed for the whole journey?
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B
Average speed = total distance ÷ total time = (90 + 120) ÷ (1.5 + 2.5) = 210 ÷ 4 = 52.5 km/h. 54 km/h is the mean of the two speeds (60 and 48), which is not the average speed. 48 km/h is the second speed only.
For the teacher: Applying, medium difficulty, standard 9.1.3
Textbook p. 173
6

Question 6

A bus leaves Seremban at 0945 and travels 255 km at an average speed of 75 km/h. At what time does it arrive?
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A
Time = 255 ÷ 75 = 3.4 h = 3 h 24 min (0.4 × 60 = 24). 0945 + 3 h 24 min = 1309. 1325 reads 0.4 h as 40 minutes.
For the teacher: Applying, medium difficulty, standard 9.1.4
Textbook p. 179
7

Question 7

A cyclist's speed changes from 6 m/s to 2 m/s in 4 s. Which statement is correct?
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D
Acceleration = (2 − 6) ÷ 4 = −1 m/s². The speed decreases, so it is a deceleration of 1 m/s². 2 m/s² comes from dividing the speed change (4 m/s) by 2 instead of by the 4 s taken.
For the teacher: Understanding, medium difficulty, standard 9.2.1
Textbook p. 180
8

Question 8

A car accelerates uniformly from rest to 90 km/h in 10 s. What is its acceleration?
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C
Acceleration = (90 − 0) ÷ 10 = 9 km/h per second. 90 forgets to divide by the time and 900 multiplies by 10.
For the teacher: Applying, low difficulty, standard 9.2.1
Textbook p. 180
9

Question 9

An acceleration is 5 m/s². What is this in km/h per second?
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B
Each second the speed rises by 5 m/s = 5 × 3.6 = 18 km/h, so the acceleration is 18 km/h per second. 1.39 divides by 3.6 instead of multiplying.
For the teacher: Applying, medium difficulty, standard 9.2.2
Textbook p. 181
10

Question 10

Diagram 1 shows the distance-time graph of a cyclist's journey. In which part of the journey is the cyclist travelling the fastest?
Distance-time graph with points O (0, 0), P (1, 12), Q (1.5, 12), R (2.5, 40) and S (3.5, 52). Distance in km, time in hours.
Diagram 1
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A
The fastest part has the steepest line. OP: 12 ÷ 1 = 12 km/h. PQ: 0 (at rest). QR: (40 − 12) ÷ 1 = 28 km/h. RS: (52 − 40) ÷ 1 = 12 km/h.
For the teacher: Analysing, medium difficulty, standard 9.1.2
Textbook p. 172
11

Question 11

A car is travelling at 36 km/h. It accelerates uniformly at 0.5 m/s² for 8 s. What is its final speed?
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C
Speed gained = 0.5 × 8 = 4 m/s = 4 × 3.6 = 14.4 km/h. Final speed = 36 + 14.4 = 50.4 km/h. 40 km/h adds 4 without changing the unit, 14.4 km/h is only the gain, and 14 km/h is the final speed in m/s (10 + 4 = 14) with the wrong unit.
For the teacher: Analysing, high difficulty, standard 9.2.3
Textbook p. 183
12

Question 12

Diagram 2 shows the speed-time graph of an object. The statements are:
I. The acceleration in the first 5 s is 2 m/s².
II. The object moves at a constant speed for 10 s.
III. The deceleration in the last 10 s is 2 m/s².
IV. The total distance travelled is 175 m.
Which statements are correct?
Speed-time graph: speed rises from 0 to 10 m/s at 5 s, stays at 10 m/s until 15 s, then falls to 0 at 25 s
Diagram 2
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D
I: 10 ÷ 5 = 2 m/s², correct. II: constant from 5 s to 15 s, which is 10 s, correct. III: the deceleration is 10 ÷ 10 = 1 m/s², so III is wrong. IV: area = ½ × (10 + 25) × 10 = 175 m, correct.
For the teacher: Evaluating, high difficulty, standard 9.2.3
Textbook p. 184

Section B: structured questions

28 marks
Answer all questions. Show your working.
13

Question 13

Use the formula for speed, distance and time to answer the following.
[1 mark] (a)Hafiz cycles 45 km in 3 hours. Find his speed in km/h.
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Tick each point you got.
[1 mark] (b)A cheetah runs at 14 m/s for 25 s. How far does it run?
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Tick each point you got.
[1 mark] (c)Sara runs 400 m at a speed of 8 m/s. How long does she take?
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For the teacher: Applying, low difficulty, standard 9.1.1
Textbook p. 171
14

Question 14

Diagram 3 shows the distance-time graphs of two toy cars, M and N, over 5 seconds.
Car M is a straight line from (0, 0) to (5, 60). Car N is a curve through (1, 6), (2, 16), (3, 30), (4, 48) and (5, 70).
Diagram 3
[1 mark] (a)Which car moves at a uniform speed? Give a reason.
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Tick each point you got.
[1 mark] (b)Find the speed of car M in m/s.
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For the teacher: Understanding, medium difficulty, standard 9.1.2
Textbook p. 172
15

Question 15

Convert speeds between units.
[1 mark] (a)Convert 108 km/h to m/s.
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Tick each point you got.
[1 mark] (b)Convert 15 m/s to km/min.
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[2 marks] (c)An aircraft flies at 900 km/h. How far does it fly in 20 seconds? Give your answer in metres.
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Tick each point you got.
For the teacher: Applying, medium difficulty, standard 9.1.3
Textbook p. 175
16

Question 16

Diagram 4 shows Ali's car journey from town P. He left at 8:00 a.m. and stopped for a rest after driving the first part of the journey.
Distance-time graph: a straight line from (0, 0) to (1.5, 90), a horizontal part from 1.5 h to 2 h, and a straight line to (4, 225). Distance in km, time in hours.
Diagram 4
[1 mark] (a)Find his speed in the first part of the journey, in km/h.
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Tick each point you got.
[1 mark] (b)For how many minutes did he rest?
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[2 marks] (c)Calculate the average speed for the whole journey.
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Tick each point you got.
For the teacher: Applying, medium difficulty, standard 9.1.3
Textbook p. 176
17

Question 17

Puan Salmah drove 168 km from town A to town B at an average speed of 84 km/h. She returned along the same road at an average speed of 70 km/h.
[2 marks] (a)Calculate the total time of the two journeys.
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Tick each point you got.
[2 marks] (b)Calculate the average speed for the whole round trip.
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This is not (84 + 70) ÷ 2 = 77 km/h, because more time is spent at the slower speed.
Tick each point you got.
For the teacher: Analysing, medium difficulty, standard 9.1.4
Textbook p. 177
18

Question 18

A motorcycle starts from rest and reaches a speed of 18 m/s in 6 seconds. It then brakes uniformly and stops in 4.5 seconds.
[1 mark] (a)Calculate its acceleration while it speeds up.
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Tick each point you got.
[2 marks] (b)Calculate its acceleration while it brakes. State the deceleration.
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Tick each point you got.
For the teacher: Applying, low difficulty, standard 9.2.1
Textbook p. 180
19

Question 19

Diagram 5 shows the speed-time graph of a train between two stations.
Speed-time graph: speed rises from 0 to 15 m/s at 10 s, stays at 15 m/s until 40 s, then falls to 0 at 60 s
Diagram 5
[1 mark] (a)Calculate the acceleration of the train in the first 10 seconds.
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Tick each point you got.
[1 mark] (b)Calculate the deceleration of the train in the last 20 seconds.
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[2 marks] (c)Calculate the distance between the two stations.
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The distance is the area of the trapezium under the graph.
Tick each point you got.
For the teacher: Analysing, high difficulty, standard 9.2.3
Textbook p. 184
20

Question 20

A delivery van must travel 90 km and be at the customer within 2 hours. It must also stop for 15 minutes to unload goods at a depot on the way. The driver is planning the speeds for the journey.
[2 marks] (a)Calculate the minimum average speed, in km/h, that the van must keep while it is driving.
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Tick each point you got.
[2 marks] (b)The first 40 km is a town road and the remaining 50 km is a highway. Choose a speed for each part, in km/h, so that the van reaches the customer on time. Show that your plan works.
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Tick each point you got.
For the teacher: Creating, high difficulty, standard 9.1.4
Textbook p. 177