1. Ch.3 Uniform Motion (勻速運動)1 2 3 4
forward

2. ? ? constant speed = constant velocity = uniform motion
If a body moves at a constant speed (固定速率)along a straight line, it is said to have uniform motion (勻速運動) .
In other words, the body moves at constant velocity (固定速度) throughout the journey.
? ?
constant speed = constant velocity = uniform motion

3. constant speed ≠ constant velocity = uniform motion
If a body moves at a constant speed along a straight line, it is said to have uniform motion.
In other words, the body moves at constant velocity throughout the journey.
constant speed ≠ constant velocity = uniform motion
constant speed along a straight line
= constant velocity

4. 3.1 Uniform Motion (勻速運動)
What is difference between average velocity (均速) and uniform velocity (勻速) ?

5. average velocity (均速) uniform velocity (勻速) 3.1 Uniform Motion (勻速運動)
= displacement / time
uniform velocity (勻速)
= constant velocity
= constant speed along a straight line

6. 3.1 Uniform Motion (勻速運動)
velocity = displacement ÷ time (v = s ÷ t)
displacement = velocity × time (s = v × t)
time = displacement ÷ velocity (t = s ÷ v)

7. Class Exercise 3.1
State whether the apple is moving with uniform motion or not. Give reasons.

8. Class Exercise 3.1
State whether the apple is moving with uniform motion or not. Give reasons.
No. It is because the speed of the apple is increasing when it falls down.

9. Class Exercise 3.1
State whether the car is moving with uniform motion or not. Give reasons.

10. Class Exercise 3.1
State whether the car is moving with uniform motion or not. Give reasons.
No. It is because the direction of the car is always changing. (not a straight line)

11. Displacement (m) Time Taken (s) Velocity (ms-1) 200 40 ( a ) ( b ) 50
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
200 40
( a )
( b ) 50 6
600
( c ) 12

12. Complete the table: Displacement (m) Time Taken (s) Velocity (ms-1)
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
200 40
( a )
(a) v = s ÷ t = 200 ÷ 40 = 5 m s-1

13. Displacement (m) Time Taken (s) Velocity (ms-1) ( b ) 50 6
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
( b ) 50 6

14. s = v × t = 6 × 50 = 300 m Displacement (m) Time Taken (s) Velocity
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
( b ) 50 6
s = v × t = 6 × 50 = 300 m

15. Displacement (m) Time Taken (s) Velocity (ms-1) 600 ( c ) 12
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
600
( c ) 12

16. t = s ÷ v = 600 ÷ 12 = 50 s Displacement (m) Time Taken (s) Velocity
Class Exercise 3.2
Complete the table:
Displacement
(m)
Time Taken
(s)
Velocity
(ms-1)
600
( c ) 12
t = s ÷ v = 600 ÷ 12 = 50 s

17. Class Exercise 3.3

18. x1 = (v)(t) = (2)(10) = 20 m x2 = (v)(t) = (2)(10) = 20 m
Class Exercise 3.3
x1 = (v)(t) = (2)(10) = 20 m
x2 = (v)(t) = (2)(10) = 20 m
x3 = (v)(t) = (2)(10) = 20 m

19. (b) What is the displacement of the car from t = 0 to
(i) t = 10 s,
(ii) t = 20 s, and
(iii) t = 30 s.

20. (b) What is the displacement of the car from t = 0 to
(i) t = 10 s,
(ii) t = 20 s, and
(iii) t = 30 s.
(i) s = x1 = 20 m
(ii) s = x1 + x2 = 40 m
(iii) s = x1 + x2 + x3 = 60 m

21. Complete the following table.
Time t / s 10 20 30
Displacement s / m

22. 40 60 (c) Complete the following table. Time t / s 10 20 3010 20 30
Displacement s / m 40 60
(d) From the data in (c), plot the graph of displacement (y-axis) against time (x-axis).

23. time /s 20 40 60 ×
displacement / m ×

24. 25 s

25. 25 s
s = 50 m

26. 25 s
s = 50 m
slope = (50 - 0) ÷ (25 - 0) = 2 m s-1

27. 25 s
s = 50 m
slope = (50 - 0) ÷ (25 - 0) = 2 m s-1
velocity