CHAPTER 25 – MEASUREMENTS Measuring time


In science, the standard unit of time is the second (s). Instruments used to measure time include stopwatches and timers. Today, the stopwatch and timer functions on a smartphone are often used to measure time.


Electronic timers connected to circuits can be used to measure time automatically. These very accurate timing systems are used at events such as the Olympics, where every hundredth of a second counts.


Eureka


Since the era of the Ancient Egyptians, time has been divided into 12 parts (12 hours of day and night). Some believe this was due to the 12 joints in the fingers – four fingers with three joints each, excluding the thumb.


:Fig. 25.2 A stopwatch


(Fig. 25.3 Electronic measurement at the Olympics


FIGURE IT OUT!


1. Convert the following into seconds: a. 1 day


b. 1 week b. days c. 1 year


2. It takes you 3 hours and 24 minutes to travel by car from Donegal to Dublin. Convert this into: a. minutes


c. seconds ? TEST TUBE


4. Name two instruments used to measure time. 5. Calculate how many seconds you will spend in science class this month, if you attend every class.


EXPERIMENTAL INVESTIGATION 25.1 How much of a delay can humans introduce to measurement?


Equipment Stopwatch


Method 1. Get the class to join hands in a circle.


2. One person with a stopwatch starts the timer when they squeeze the hand of the person to their left.


3. Each person squeezes the hand of the person to their left as they feel their right hand being squeezed.


4. When it makes it all the way around the circle and back to the person with the stopwatch, they stop the timer.


6. Repeat twice more and calculate the average. j Go to page 69 of your Experimental Investigations Log to write up this investigation.


:Fig. 25.4 To show how much of a delay humans introduce to measurement


5. Divide this time by the number of people in the experiment to find the average human delay caused by each person.


Elements of Science 239


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