NCERT Solutions Ganita Prakash (Part 2) Chapter 5 –120Space Jam: A Traffic Problem in the Future? — In-text Questions
Book page 119 Updated on2026-09-05
Q1.
What could be the possible method used to derive this data? Discuss.
Answer
Every launch that reaches orbit is tracked and catalogued. Space agencies and defence radar networks record each object put into orbit — satellites, probes, landers, crewed spacecraft and space-station parts — and international registers keep a running list with its launch date and launching country. Counting the entries for each year gives the worldwide figure; sorting them by country gives the separate lines for the USA, China and Russia.
Why this matters for reading the graph: the counts come from an official register, so an object that never reached orbit, or one that was never declared, would not appear. The graph also counts objects, not launches — a single rocket carrying 60 small satellites adds 60 to the count. That alone explains much of the steep climb after 2019, when large satellite constellations began going up.
Q2.
Which of the following statements are valid inferences? • From 2012 till 2024, the worldwide count of space object launches increased every year. • USA is a major contributor in the years 2022 – 24, launching about 3/4th of the worldwide count. • Nepal did not launch any object in the period 2012 – 24. • The combined count of object launches by China and Russia in 2024 is about 400.
Answer
“Increased every year” — not valid. The overall climb is steep, but the world line dips in a few places: it falls slightly from 2014 to 2015 and again to 2016, dips from 2017 to 2018, and falls from about 2900 in 2023 to about 2800 in 2024. ‘Every year’ is a much stronger claim than ‘overall’.
“USA launched about 3/4th in 2022–24” — valid. Reading the two lines: in 2022 about 1950 out of 2500; in 2023 about 2250 out of 2900; in 2024 about 2280 out of 2800. Those fractions are roughly 0.78, 0.78 and 0.81 — close to three-quarters.
“Nepal did not launch any object” — not valid. The graph has only four lines: World, United States, China and Russia. Nepal is simply not shown. A graph that does not mention something says nothing about it, and you cannot turn silence into evidence.
“China and Russia together about 400 in 2024” — valid. Reading the two lower lines at 2024 gives roughly 300 for China and roughly 110 for Russia, a total of about 410 — ‘about 400’ is a fair reading.
The habit to build: before accepting a statement, ask which line and which points on the graph support it. The Nepal claim fails not because it is false in the world but because this graph cannot decide it — the commonest mistake in reading data.
Q3.
Identify two consecutive years where the worldwide count increased by 2 times or more.
Answer
Two such jumps show up on the world line:
2016 → 2017: about 245 → about 505
505 ÷ 245 ≈ 2.1 times ✓
2019 → 2020: about 610 → about 1280
1280 ÷ 610 ≈ 2.1 times ✓
No other consecutive pair comes close: even the big rise from 2021 to 2022 is roughly 1810 to 2500, only about 1.4 times.
Careful: ‘increased by 2 times or more’ is about the ratio, not the gap. From 2021 to 2022 the count rose by about 690 objects, a larger gap than the 260 gained between 2016 and 2017 — yet only the smaller gap counts here, because 260 on top of 245 is a doubling and 690 on top of 1810 is not. On a graph, steepness shows the gap; you have to compare the two heights to see the ratio.