Speed and Acceleration

Chapter 9

SPEED AND
ACCELERATION

Pn Sazazila Abdullah

CONTENTS

WHY STUDY THIS CHAPTER ?

WORD LINK

9.1 Speed
9.11 Speed as a rate

9.1 Speed
9.1.1 Speed as a rate

Speed  Dis tan ce
Time

km / h, m / s km per hour , m per sec ond

9.1 Speed
9.1.1 Speed as a rate

Solution:

Speed  100m
5 min

 20 m / min

9.1 Speed
9.1.2 Uniform and non-uniform speed

uniform speed

9.1 Speed
9.1.2 Uniform and non-uniform speed

non-uniform
speed .

speed

9.1 Speed
9.1.2 Uniform and non-uniform speed

Elevator lift .
Uniform
speed .

9.1 Speed
9.1.2 Uniform and non-uniform speed

Escalator.
Uniform
speed .

Example 2

Farid drove a trailer for 170 km within the first 2

hours and 190 km within the next 4 hours . Did

Farid drive the trailer at a uniform speed? Explain.

Solution:  170km
Speed for the first 2 hours 2h

 85 km / h

Speed for next 4 hours  190km
4h

 47.5 km / h

Example 2
Farid drove a trailer for 170 km within the first 2
hours and 190 km within the next 4 hours . Did
Farid drive the trailer at a uniform speed? Explain

Solution:
Therefore , the speed of the trailer is non-uniform .

9.1 Speed
9.1.3 Average speed

9.1 Speed
9.1.3 Average speed

Average speed  Total dis tan ce
Total time

Example 3
A bus departs from Puchong at 0825 and
arrives in Perai at 1345 . If the total distance
travelled is 354 km , calculate the average
speed in km/h.

Solution:
Total distance = 354 km
Total time taken = 1345 - 0825

= 5 hours 20 min

Example 3

A bus departs from Puchong at 0825 and

arrives in Perai at 1345 . If the total distance

travelled is 354 km , calculate the average

speed in km/h.
Solution:
Average speed = Total dis tan ce

Total time

 354 km
5.33 h

 66.42 km / h

Example 4
The speed limit on Jalan Persekutuan is 90 km/h .
Convert this speed to m/s .

Solution: 90 km
90 km/h =
1h

 901000 m
1 3600 h

 25 m / s

Example 5
Convert 120 m/s to km/min.

Solution: 120 m
120 m/s = 1s

 120 1000 km
1 60 min

 0.12 km
0.017 min

 7.06 km / min

9.2 Acceleration
9.2.1 Acceleration and deceleration

9.2 Acceleration
9.2.1 Acceleration and deceleration

9.2 Acceleration
9.2.1 Acceleration and deceleration

change of speed  final speed  initial speed
time time

km / h2 , m / s2 km / h per hour , m / s per sec ond

Example 6
A racing car accelerates from a stationery state
and reaches a speed of 120 km/h in 6 seconds.
Calculate the acceleration in km / s2 .

Solution:
Changes of speed = 120 km/h - 0 km/h = 120 km/h

120 km  120 km
1 h 60 60 s

 0.033 km / s

Example 6
A racing car accelerates from a stationery state
and reaches a speed of 120 km/h in 6 seconds.
Calculate the acceleration .

Solution: 0.033 km / s
Acceleration = 6s

 0.0056 km / s2

9.2 Acceleration
9.2.2 Unit conversion

Example 7

Convert 120 km / h2 to km/h per minute.

Solution: 120 km / h

h

 120 km / h
60 min

 2 km / h per min ute

9.2 Acceleration

Example 8
Calculate the acceleration if the speed of a boat
decrease from 70 km/h to 40 km/h in 5 minutes .

Solution:
acceleration= 40  70 km / h

5 min
 6km / h per min ute

9.2 Acceleration

Example 8
Calculate the acceleration if the speed of a boat
decrease from 70 km/h to 40 km/h in 5 minutes .

Solution:  6km / h per min ute
deceleration=

If question ask
deceleration

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