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Unit review: number ray and motion
Textbook: Part 2, unit review, pp. 52–53
GoalMixed practice on the number ray and motion.
New words
review · takrorlashscale · shkaladistance · masofaspeed · tezlik
Explanation
This lesson wraps up the unit: scales and the value of a division, coordinates and the unit segment, distance between points, S = v × t, opposite motion (v₁ + v₂), catch-up motion (v₂ − v₁) and delayed start. In each problem first decide the kind of motion and then pick the formula.
Worked examples
6 parts between 0 and 90: a division is 90 : 6 = 15.
450 km apart, 60 and 90 km/h towards each other: 450 : 150 = 3 h.
Class activity
“Unit quiz”: groups take cards, name the kind of motion, state the formula and solve the problem.
Practice
1
On a number ray there are 6 equal parts between 0 and 90. What is the value of one division?
15
2
The unit segment is e = 4 m and the point is C(9). How many m is OC?
36
3
Trains leave cities 450 km apart at 60 and 90 km/h towards each other. After how many hours do they meet?
3
4
The gap is 36 km. The cyclist behind rides at 14 km/h and the one ahead at 8 km/h. After how many hours does he catch up?
6