Ch.1 Distance (Ch.1 Distance ( 距離距離 ) & Displacement () & Displacement ( 位位移移 ))

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Tai Wai Station

Kowloon Tong Station

displacement 4 km to the northdistance

4.4 km

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Class Exercise 1.1

Distance travelled = ?

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Class Exercise 1.1

Distance travelled = 12 + 98 + 70 = 180 m

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Displacement (位移 ) = change in position

The change in position is a straight line joining the start position (起點 ) and the end position (終點 ).

Magnitude (量值 ): Length of the straight line joining the start position and the end position.

Direction (方向 ): Direction of the straight line from the start position to the end position.

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North ( 北 )

West ( 西 )

East ( 東 )

South ( 南 )

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N

40°

Direction = ?

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N

40°

Direction = 50°

50 °

E

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N

60°

Direction = ?

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N

60°

Direction = 150°

S

E

90° + 60° = 150°

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N

40°

Direction = ?

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N

40°

Direction = 230 °

S

W

50°

90° + 90° + 50° = 230 °

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N

40°

Direction = ?

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N

40°

Direction = 320°

W270° + 50° = 320°

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Class Exercise 1.2

Magnitude of displacement = ?Direction of displacement = ?

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Class Exercise 1.2

Magnitude of displacement = 128 mDirection of displacement = 180º + 40° = 220°

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Class Exercise 1.3 (a) & (b)

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Class Exercise 1.3 (a) & (b)

6 m

East (90°)

6 m

East

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Class Exercise 1.3 (c) & (d)

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Class Exercise 1.3 (c) & (d)

6 m 6 m

East East

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Note: If the starting position and the end position are the same, the displacement is the same.

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Class Exercise 1.4 (a)

You walk from LPSMC to the Entrance C of the Tsuen Wan MTR station. Find the magnitude and direction of your displacement.

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Class Exercise 1.4 (a)

6.2 cm

3.2 cm

Magnitude = ?Direction = ?

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Class Exercise 1.4 (a)

6.2 cm

3.2 cm

Magnitude = (6.2 ÷ 3.2 ) × 100 = 194 mDirection = 180° + 77° = 257° (S 77 W)

78°

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Class Exercise 1.4 (b)

You meet your friend, Tommy, at Entrance C. He is going to the YMCA in Luk Yeung Sun Chuen. What is his displacement from Entrance C to the YMCA?

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Class Exercise 1.4 (b)

3.2 cm

Magnitude = ?Direction = ?

3.7 cm

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Class Exercise 1.4 (b)

3.2 cm

Magnitude = (3.7 ÷ 3.2 ) × 100 = 116 m

Direction = 50° (N 50 E)

3.7 cm

50°

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Class Exercise 1.5

Mr. Chan walks 3 m from A to the East. He turns 90 and walks 6 m to the South. Finally he walks a further distance of 9 m to the West.

(a) In the space below, draw arrows to represent these displacements. (Use 1 cm to represent 1 m.)

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Class Exercise 1.5 (a)

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Class Exercise 1.5 (a)

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Class Exercise 1.5 (b)

(b) direction and magnitude of the total displacement = ?

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Class Exercise 1.5 (b)

magnitude of the total displacement = 8.5 mdirection of the total displacement = 180° + 45° = 225°

45°

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Class Exercise 1.6 (a)

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Class Exercise 1.6 (a)

12 m East

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Class Exercise 1.6 (a)

12 m

6 m

East

East

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Class Exercise 1.6 (a)

12 m

6 m

18 m

East

East

East

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Class Exercise 1.6 (b)

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Class Exercise 1.6 (b)

S

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Class Exercise 1.6 (b)

-10 m or 10 m (West)

S

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Class Exercise 1.6 (b)

-10 m or 10 m (West)

8 m (East)

S

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Class Exercise 1.6 (b)

-10 m or 10 m (West)

8 m (East)

28 m

S

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Class Exercise 1.7

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Class Exercise 1.7

distance = 3 + 4 = 7 m

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Class Exercise 1.7

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Class Exercise 1.7

53°

magnitude = 534 22

direction = 90° + 37° = 127° (S 53 E)

m

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Class Exercise 1.7

62°

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Class Exercise 1.7

62°

P

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Class Exercise 1.7

-4.0 m or 4.0 m (West)

3.0 m (South)

62°

P

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Scalar (無向量 )Vector (向量 /矢

量 )

has magnitude (量值 ) only.

has both magnitude and direction.

Example:• distance (距離 )• time (時間 )• temperature (溫度 )• speed (速率 )• ……

Example:• displacement (位移 )• velocity (速度 )• acceleration (加速度 )• force ( 力 )• ……

1.3 Scalar and Vector

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Homework: Assignment Book 1. Chapter 1: Distance & Displacement

Q.1 – Q.6 (p.1-5) 2. Deadline: 2011 - - ____