CBSE Experiment Measurement of Time

What is Time?

Time relates to the fundamental physical quantities along with length and mass. Time can be measured using any occurrence that repeats after an equal amount of time. There are a lot of such repeating phenomena in nature. Such as the motion of the earth on its axis, the motion of the Earth around the Sun, and the motion of a wall clock or a pendulum. Projection of satellites is only possible because of precise measurement of time.

What is Second?

Previously, the second was specified as \[\dfrac{1}{{86400}}\]of the mean solar day, or the average time it takes for the Earth to rotate on its axis with respect to the Sun. 

Table of content

• Aim

• Theory

• Procedures and observations

• Result

Aim 

To measure time using the different devices.

Apparatus Required 

• Clocks

• Watches

• Ticker Tape Timer 

Theory 

Second is the SI unit of time (s). It has a scalar value. The precise duration of 9,192,631,770 radiation cycles associated with the change between the two hyperfine levels of the ground state of the caesium-133 atom is what defines the standard unit of time, the second (s).

Devices Used to Measure Time

1. Sundial - A sundial consists of a dial plate with hour lines engraved on it and a gnomon stick that sticks out at an angle. As the sun moves across the sky, it casts a shadow on the dial plate, which displays the time. 

Sundial

2. Pendulum - Previously, a basic pendulum was utilised, which would oscillate at a steady pace as long as the bob's weight and the pendulum's length remained unchanged.

Pendulum

3. Clocks - These are mechanical devices to measure time. Its two hands' tips revolve in a circular motion that is graduated to represent hours and minutes.

Clocks

4. Atomic clocks - Atomic clocks have been created using atomic vibration. The clocks they control barely show a fraction of a second variation over thousands of years because these atomic vibrations are so consistent. 

Procedures and Observations:

1. Measurement of Time by Clocks

The start time is either noted or the clock is configured to start at a specific time. Following this, the time event is allowed to take place, and the end time is recorded. The difference gives the necessary amount of time.

Accuracy - \[ \pm 1s\]

2. Measurement of Time by Stopwatches

The stopwatch is started concurrently with the time event. The stopwatch is stopped at the end of the event, and the time is recorded. The reading gives the required time interval. Some accurate stopwatches are more accurate because they are electrically tied to the time event.

Accuracy - \[ \pm 1s\](For laboratory investigations, a human reaction time restricts the stopwatch's accuracy to 0.1–0.4 s. Records with up to two decimal places should not be used.)

3. Measurement of time by Ticker Tape Timer

The tape is tied to an object, and it is possible to determine its motion from the dots on the tape.

The best way to demonstrate how to determine the state of motion from the resulting tape is with an example. The three tapes in the above diagram, labelled X, Y, and Z, each measure 1 m from start to finish. A ticker tape timer with a 0.1-second time interval creates the dots.

Ticker Tape Timer

• The dots are uniformly spaced for X. The distance between each dot is 0.2 m because the length is 1 m. So, the calculations for speed will be,

\[Speed = \dfrac{{Dis\tan ce}}{{time}} = \dfrac{{0.2}}{{0.1}} = 2 m/s\]

Consequently, X stands for the tape from an object that is moving continuously.

• As time passes for Y, the distance between the dots widens. The time in the calculation above is fixed because the dots are made with a predetermined time interval. As the gap between the dots widens, we'll experience an increasing speed. Consequently, Y represents the tape from an accelerating object.

• As time passes for Z, the distance between the dots gets smaller. Z represents the tape from an object that is decelerating using the same logic as above.

Results 

Measurements of time taken by different devices show that the number of intervals is equal every time.

Precautions

• Check the tape to see if you can distinguish each distinct dot and the space between them.

• The distance between the start and the stop should be measured in dot-to-dot spacing. 

• Use a stopwatch or stopclock, along with a new piece of tape.

Lab Manual Questions

1. According to the experiment, mention the most common feature in all clocks.

Ans: All clocks have a common feature in that they all display periodic motion.

2. According to the experiment, what is the accuracy of time when it (time) is being measured by clocks and stopwatches?

Ans:  \[ \pm 1s\]

3. What happens to the speed of the ticker tape when the gaps between dots on the ticker tape increase?

Ans: The speed will increase when the dots on the ribbon of the ticker tape.

4. What makes a watch different from a clock? 

Ans: A clock is large. One second is the lowest count. The size of a watch is smaller. Its minimum count is 0.1 or 0.2 seconds.

Viva Questions

1. Calculate the number of hours in a year.

Ans: There are 365 days in a year

1 day=24 hours

\[{\rm{For 365 days  =  24 h}} \times 365 days = 8760 hrs\]

2. Describe how time was kept in the absence of pendulum clocks.

Ans: Before the pendulum was discovered, sundials, water clocks, and sand clocks were used.

3. A quartz clock or a pendulum clock from the two options provided. Mention what kind of clock requires an electric cell to operate.

Ans: Electric cells are needed for a quartz clock to function.

4. Identify the earliest time scale that was used to measure it.

Ans: The oldest ancient unit of time used for measurement is the solar day.

5. Describe the method used to calculate a month.

Ans: The interval between each new moon determines a month's duration.

6. Describe briefly how you will determine which object travels quickly and which is moving slowly.

Ans: When one thing moves farther in the same amount of time relative to another, we can say that the other object travels more slowly.

7. How would you determine what time it is if there was no clock?

Ans: By seeing the sun's shadow, we can determine the time of day without using a clock. For example, the sun's shadow is shorter at midday than at dusk.

8. Name a device which is used to measure short intervals of time.

Ans: The device used to measure the short intervals of time is a chronoscope. 

9. Which watch will you use to precisely calculate brief intervals of time?

Ans: Extremely brief time intervals, of the order of 10(-9) seconds, are measured by atomic clocks and watches (nanoseconds)

The smallest time that a digital watch can measure is around 0.01 seconds. Digital stopwatches are used to measure minutes and seconds.

10. How would you determine what time it is if there was no clock?

Ans: By seeing the sun's shadow, we can determine the time of day without a clock. For example, the sun's shadow is shorter at midday than at dusk.

Practical Based Questions

1. How does the sundial work?

1. The shifting location of the moon in the sky creates a shadow at different spots designated on the sundial, which reveals the time of the day.

2. The sundial, which displays the time of day, uses the shadows it casts at various locations to indicate how the sun is positioned in the sky.

3. A shadow is cast at various locations indicated on the sundial that indicates the time of day due to the Pole Star's shifting position in the sky.

4. None of the above

Ans: B) The sundial, which displays the time of the day, uses the shadows it casts at various locations to indicate how the sun is positioned in the sky.

2. What does the sundial measure?

1. Distance

2. Area

3. Speed

4. Time

Ans: D) time

4. The time of the sundial is dependent on,

1. Position of the pole star

2. Position of the Moon

3. Position of the Sun

4. None of the above

Ans: C) Position of the Sun

5. Which axis does the dependent variable lie in general?

1. y-axis

2. x-axis

3. On any axis

4. None of the above

Ans: A) y-axis

6. what is the relationship between these quantities if we indicate speed by S, the distance by D, and time by T?

1. \[T = \dfrac{S}{D}\]

2. \[S = \dfrac{D}{T}\]

3. \[S = \dfrac{T}{D}\]

4. \[S = D \times T\]

Ans: B) \[S = \dfrac{D}{T}\]

7. Which device keeps track of how far a car has travelled?

1. Manometer

2. Motometer

3. Odometer

4. Speedometer

Ans: C) Odometer

8. What is the correct symbol to represent the speed of an object?

1. 6 m/s

2. 6 ms

3. 6 ms-2

4. None of the above

Ans: A) 6 m/s

9. Which of the following is not a valid method for measuring time?

1. Simple Pendulum

2. A leaking tap

3. Blinking of eyes

4. None of the above

Ans: C) Blinking of eyes

10. Which of the following element(s) is/are taken into account when calculating time using a sundial?

1. The wind's velocity and direction.

2. shadow cast by the sundial in terms of length.

3. the sundial's shadow's direction of shadow.

4. Both B and C

Ans: D) Both B and C

11. Out of the following options, which one calculates time accurately?

1. Pendulum Clock

2. Sundial

3. Quartz Watch

4. None of the above

Ans: C) Quartz Watch

12. Which of the following options is not true about Sundial?

1. They operate according to the Sun's position.

2. At night, they are more accurate.

3. On cloudy days, sundial accuracy is marginally higher.

4. Both B and C

Ans:  D) Both D and C

13. The time is measured by clocks and watches, which are based on

1. Rotational motion

2. Circular motion

3. Periodic motion

4. Rectilinear motion

Ans: C) Periodic motion

14. The tool used to measure time intervals in sporting events is known as

1. Quartz watch

2. Wristwatch

3. Stopwatch

4. None of the above

Ans: C) Stopwatch

Conclusion

The duration between the start and end of an event can be measured with time using different time-measuring tools. Interestingly, time was measured in the past using sundials, sand clocks, and water clocks; however, it is now measured with digital, mechanical, quartz, and atomic clocks, which can be separated by their precision and accuracy. From this experiment, students can understand that the time has equal intervals, and the accuracy of each interval is approximately the same even when various instruments are measuring it.