Basic Science Solutions for Class 7 Science Chapter 1 The Language Of Chemistry are provided here with simple step-by-step explanations. These solutions for The Language Of Chemistry are extremely popular among Class 7 students for Science The Language Of Chemistry Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of Class 7 Science Chapter 1 are provided here for you for free. You will also love the ad-free experience on Meritnationâ€™s Basic Science Solutions. All Basic Science Solutions for class Class 7 Science are prepared by experts and are 100% accurate.

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A known fixed quantity is a unit of measurement. We compare an unknown quantity that we wish to measure with a fixed quantity.

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Speed of a body is defined as the distance travelled by the body in unit time. Its SI unit is metres/second (m/s).

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A body is said to be in motion when its position changes with time.

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Stopwatches have electronic switches which can be used to stop or start these watches. This helps in measuring time intervals more accurately than ordinary watches which indicate continuous passage of time. This is how stopwatches are different from ordinary watches.

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The periodic motion of pendulums makes them suitable for making clocks.

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The time period of a pendulum is the time taken by it to complete one oscillation.

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One factor that determines the time period of a pendulum is the length of the pendulum.

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A moving body is said to be in uniform motion when its speed remains constant i.e., it covers equal distances in equal intervals of time.

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(a) 90 m

(b) 100 kg

(c) 10 s

(d) 50 kg

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$\text{Timeinminutes=20}\phantom{\rule{0ex}{0ex}}\mathrm{T}\text{imeinhours=}\frac{20}{60}=\frac{1}{3}\phantom{\rule{0ex}{0ex}}\mathrm{Distance}=15\mathrm{km}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\mathrm{Speed}=\raisebox{1ex}{$\mathrm{Distance}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{Time}$}\right.\phantom{\rule{0ex}{0ex}}\mathrm{Speed}\mathrm{in}\mathrm{km}/\mathrm{h}=\frac{\mathrm{Distance}\mathrm{in}\mathrm{kilometres}}{\mathrm{Time}\mathrm{in}\mathrm{hours}}\phantom{\rule{0ex}{0ex}}=\frac{15}{1/3}=\frac{15\times 3}{1}=45\mathrm{Km}/\mathrm{h}\phantom{\rule{0ex}{0ex}}\mathrm{Time}\mathrm{in}\mathrm{seconds}=20\times 60=1200\mathrm{s}\mathrm{Distance}\mathrm{in}\mathrm{m}=15\times 1000=15000\mathrm{m}\mathrm{Speed}\mathrm{in}\mathrm{m}/\mathrm{s}=\frac{\mathrm{Distance}\mathrm{in}\mathrm{metres}}{\mathrm{Time}\mathrm{in}\mathrm{seconds}}\mathrm{Speed}\mathrm{in}\mathrm{m}/\mathrm{s}=\frac{15000}{1200}=12.5\mathrm{m}/\mathrm{s}$

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$\mathrm{Distance}=400\mathrm{km}\phantom{\rule{0ex}{0ex}}\mathrm{Speed}=50\mathrm{km}/\mathrm{h}\phantom{\rule{0ex}{0ex}}\mathrm{Average}\mathrm{speed}=\frac{\mathrm{Total}\mathrm{distance}\mathrm{travelled}}{\mathrm{Total}\mathrm{time}\mathrm{taken}}\phantom{\rule{0ex}{0ex}}\mathrm{Time}=\frac{\mathrm{Distance}}{\mathrm{Speed}}\phantom{\rule{0ex}{0ex}}\mathrm{Time}=\frac{400\mathrm{km}}{50\mathrm{km}/\mathrm{h}}\phantom{\rule{0ex}{0ex}}\mathrm{Time}=8\mathrm{hours}$

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$\mathrm{Average}\mathrm{speed}=40\mathrm{km}/\mathrm{h}\phantom{\rule{0ex}{0ex}}\mathrm{Time}=6\mathrm{hours}\phantom{\rule{0ex}{0ex}}\mathrm{Speed}=\frac{\mathrm{Distance}}{\mathrm{Time}}\phantom{\rule{0ex}{0ex}}\mathrm{Distance}=\mathrm{Speed}\times \mathrm{Time}\phantom{\rule{0ex}{0ex}}\mathrm{Distance}=40\times 6\phantom{\rule{0ex}{0ex}}=240\mathrm{km}$

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$\mathrm{Given}:\phantom{\rule{0ex}{0ex}}\mathrm{Distance}=3\mathrm{m}\phantom{\rule{0ex}{0ex}}\mathrm{Time}=4\mathrm{s}\phantom{\rule{0ex}{0ex}}\therefore \mathrm{Speed}=\frac{\mathrm{Distance}\left(\mathrm{D}\right)}{\mathrm{Time}\left(\mathrm{T}\right)}\phantom{\rule{0ex}{0ex}}\mathrm{Speed}=\frac{3\mathrm{m}}{4\mathrm{s}}(\mathrm{since},\mathrm{D}=3\mathrm{m}\mathrm{and}\mathrm{T}=4\mathrm{s})\phantom{\rule{0ex}{0ex}}\therefore \mathrm{Speed}=0.75\mathrm{m}/\mathrm{s}$

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