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Measurement of Time and Motion - Measurement of Time

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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In ancient times, people measured time using natural events that repeat regularly, such as the interval between one sunrise and the next (a day) or one full moon to the next (a month).

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Modern time measurement is based on periodic motion, which is motion that repeats itself at regular intervals of time.

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A simple pendulum is a common example of periodic motion. It consists of a small metallic ball, called a bob, suspended from a rigid stand by a thread.

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The motion of the pendulum from its mean position to one extreme, then to the other extreme and back to the mean position is called one oscillation.

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The time taken by the pendulum to complete one oscillation is called its Time Period (TT).

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The SI unit of time is the second (ss). Other commonly used units are minutes (minmin) and hours (hh).

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Clocks and watches today typically use an electronic circuit with a quartz crystal, providing much higher accuracy than older mechanical clocks.

📐Formulae

Time Period(T)=Total Time TakenNumber of Oscillations\text{Time Period} (T) = \frac{\text{Total Time Taken}}{\text{Number of Oscillations}}

1 hour=60 minutes1 \text{ hour} = 60 \text{ minutes}

1 minute=60 seconds1 \text{ minute} = 60 \text{ seconds}

1 hour=3600 seconds1 \text{ hour} = 3600 \text{ seconds}

💡Examples

Problem 1:

A student observes that a simple pendulum takes 32 s32\text{ s} to complete 2020 oscillations. What is the time period of the pendulum?

Solution:

Time Period=3220Time Period=1.6 s\begin{array}{r} \text{Time Period} = \frac{32}{20} \\ \text{Time Period} = 1.6\text{ s} \end{array}

Explanation:

The time period is calculated by dividing the total time recorded by the number of oscillations completed. Here, 3220\frac{32}{20} gives a result of 1.6 s1.6\text{ s} per oscillation.

Problem 2:

Convert 2 hours2\text{ hours} and 15 minutes15\text{ minutes} into total seconds.

Solution:

2×3600=7200 s15×60=900 s7200+900=8100 s\begin{array}{r} 2 \times 3600 = 7200 \text{ s} \\ 15 \times 60 = 900 \text{ s} \\ \hline 7200 + 900 = 8100 \text{ s} \end{array}

Explanation:

First, convert hours to seconds by multiplying by 36003600. Then, convert minutes to seconds by multiplying by 6060. Finally, add both values to get the total time in seconds.