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Learn the difference between average velocity and uniform velocity, and how to calculate displacement, time, and velocity in uniform motion. Includes class exercises and examples.
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forward 1 2 0 3 4 Ch.3 Uniform Motion (勻速運動)
3.1 Uniform Motion (勻速運動) • 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
3.1 Uniform Motion (勻速運動) • If a body moves at a constant speedalong a straight line, it is said to have uniform motion. • In other words, the body moves at constant velocitythroughout the journey. constant speed ≠ constant velocity = uniform motion constant speed along a straight line = constant velocity
3.1 Uniform Motion (勻速運動) What is difference between average velocity (均速)and uniform velocity (勻速)?
3.1 Uniform Motion (勻速運動) average velocity (均速) = displacement / time uniform velocity (勻速) = constant velocity = constant speed along a straight line
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)
Class Exercise 3.1 State whether the apple is moving with uniform motion or not. Give reasons.
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.
Class Exercise 3.1 State whether the car is moving with uniform motion or not. Give reasons.
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)
Class Exercise 3.2 Complete the table:
Class Exercise 3.2 Complete the table: (a) v = s ÷ t = 200 ÷ 40 = 5 m s-1
Class Exercise 3.2 Complete the table:
Class Exercise 3.2 Complete the table: s = v × t = 6 × 50 = 300 m
Class Exercise 3.2 Complete the table:
Class Exercise 3.2 Complete the table: t = s ÷ v = 600 ÷ 12 = 50 s
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
(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.
(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
(c) Complete the following table. (d) From the data in (c), plot the graph of displacement (y-axis) against time (x-axis).
displacement / m × 60 × 40 × 20 time /s × 10 20 30
25 s s = 50 m
25 s s = 50 m slope = (50 - 0) ÷ (25 - 0) = 2 m s-1
25 s s = 50 m slope = (50 - 0) ÷ (25 - 0) = 2 m s-1 velocity