*Measurement of time-
-time-the interval between two instances or events is called time.
-SI unit of time is second.
-symbol is s.
-def.
1 second is defined as 1/86400 part of a mean solar day.
Bigger unit of time:
1 minute=60 seconds
1hour=60 minutes
=60×1 minute
=60×60s
=3600 s
1 day=24×1 hour
=24×3600 s
=86400 s
1year=365×1day
= 365× 86400s
=31536000s
≈3.15×10⁷ s
*Devices for measuring time:
1. A pendulum clock-
Time is measured by making use of the time taken by a pendulum to complete one oscillation.
-oscillation-one complete to and fro motion of a pendulum is known as one oscillation.
-time period-time taken by a pendulum to complete its one oscillation is called as it's time period.
-the time period of a seconds pendulum is 2 second.
-•The seconds arm moves by one small division when the pendulum moves from one extreme to the other extreme.i.e., 1s
•the minutes are moves by a small division and the seconds arm completes one round.i.e., 60s
•the hours arm moves by 5 small divisions when the minutes arm complete one round.i.e.,1 h.
2.A watch-
-the seconds arm is driven by a wound up spring.
Measuring devices for short time interval:
1. Stop clock
2. Stopwatch
•they have arrangements to start, to stop and to reset at zero.
•electronic stopwatch-
-electronic stopwatch can measure time intervals accurately upto 0.01 seconds.
-electronic stopwatch is used for measuring the timings of athletic activities.
*Measurement of temperature:
-the temperature is the measure of degree of hotness or coldness of an object.
-SI unit of temperature is Kelvin.
-symbol is K.
-ice point is 273.15 K
-steam point is 373.15 K
-the number of divisions between ice point and steam point are 100.
-some other units of temperature are:
1.Degree Celsius
-symbol is °C
•given by scientist Andrews Celsius.
- it is used to measure days maximum & minimum temperature.
- ice point is zero degree celsius.
-steam point is 100 degree Celsius.
-the number of divisions between ice point and steam point are 100.
•one degree on Celsius scale is equal to 1.8 degree on fahrenheit scale.
•degrees celsius also called as centigrade scale because it has 100 divisions between the ice point and steam point in the Celsius scale.
2. Degree fahrenheit
-symbol is °F.
•named after the scientist G.D. Fahrenheit
- it is used to measure body temperature of a person.
- Normal body temperature = 98.6°F
-ice point is 32 degree fahrenheit.
-steam point is 212 degree fahrenheit.
-the number of divisions between steam point and ice point are 180.
*Relationship between three temperature scales:
(Symbol -ice point)/ number of divisions
(°C - 0 )/100 = (°F - 32)/180 = (K- 273.15)/100
(°C - 0 )/5 = ( °F - 33 )/18 = (K- 273.15 )/5
Relationship between degree Celsius and degree fahrenheit scales:
(°C - 0 )/5 = (°F - 32)/18
⇒ (°C ) = 5×( °F - 32 )/18
(°F- 32)/18 = °C/5
⇒(°F - 32) =18×°C/5
⇒°F = 18×°C/5 + 32
Relationship between degree Celsius and Kelvin:
(°C - 0 ) = ( K - 273.15)
⇒ ° C = 5 × (K- 273.15)/5
(K - 273.15)/5 = ( °C - 0)/5
⇒ ( K - 273.15) = 5 × ° C/5
⇒ K = 5 × °C/5 + 273.15
Relationship between degree Fahrenheit and Kelvin scale:
(°F - 32)/9 = ( K - 273.15)/5
⇒(°F - 32) = 9× (K - 273.15)/5
⇒°F = 9× (K- 273.15)/5 + 32
(K - 273.15)/5 = ( °F - 32)/9
⇒(K - 273.15) = 5 × (° F - 32)/9
⇒K = 5×( °F - 32)/9 + 273.15
*Device used to measure the temperature of an object:
-temperature is measured by device called thermometer.
1. Laboratory thermometer:
_description-
-glass capillary tube with a bulb at one end.
-the bulb filled with Mercury.
-the system has markings from - 10°C to 110°C.
| •range of a laboratory thermometer=upper fixed point - lower fixed point |
= 110°C - (-10°C)
= 110°C + 10°C
= 120°C
•it is used in labs for measuring temperature during experiments, Daily maximum- minimum temperature of the day etc.,
2. Clinical thermometer:
-doctors use special thermometer called the clinical thermometer for measuring the temperature of the patient's body.
•description:
-it has markings from 35 degree celsius to 42 degree Celsius.
-slight bend or king in the stem just above the bulb called as constriction to prevent the Mercury from falling back all by itself.
-red arrow on it indicates the normal temperature of a person= 37°C or 98.6°F
-clinical thermometers marked in °F have markings from 95°F to 110°F.
Measuring the temperature of a patient's body with clinical thermometer:
-1. Clinical thermometer is slightly jerked to bring the level of Mercury in its capillary tube below the mark 37 °C.
2.thermometer bulb is kept below the tongue or under the arms pit of the patient for about a minute.
3. It is taken out and reading is noted.
4. If the reading is more than or less than 37°C,then then person is abnormal or suffering from some illness.
*clinical thermometer cannot measure the temperature of boiling water because it can measure only up to 42 degree Celsius where as the temperature of boiling water is hundred degree Celsius.
•digital thermometers are preferred instead of Mercury thermometer . Because mercury is highly toxic for human beings.
*Physical quantities:
-whether a physical quantity depends on each other or not it can be divided into two :
1. Fundamental quantities:
-a physical quantity which does not depend or related to other physical quantities are called as fundamental quantities. Example length, mass, time, temperature etc.,
2. Derived quantities:
-physical quantities which are expressed in terms of the other measurable fundamental quantities like length, mass, time, etc., are called derived quantities. Example area, volume, speed, density, force, weight,etc.,
-area= length×breadth
- volume= length×breadth×height
-speed= distance/time.
*Measurement of area:
-area-the total surface occupied by an object is called its surface area or simply the area.
-it can be expressed in terms of the product of two measurements in length.
-SI unit is m²
-CGS unit is cm²
-area of regular shapes-(formula method)
1. Area of square=l×l
2. Area of a rectangle= l× b
3. Area of a triangle=1/2 × base×height.
4. Area of a circular lamina of radius r
=πr², π =22/7 or π=3.14
•area of irregular surfaces (By graphical method)
-the area of regular or irregular surface can be obtained by using a graph paper.
Procedure:
1. Place the given surface on a graph paper.
2. Count the number of complete squares.
3.Add the number of incomplete squares recharge half or more than half within the outline.
4. Area of one box is 1 cm square.
More than half boxers •
Approximate area=(number ofcomplete squares +number of half hour more than half of incomplete square)×area of one square
Multiple and submultiple units of area:
-the area of a big agricultural field or a city are measured by using bigger units of area such as decameter square (are), hectare, square kilometre etc.,
1 decameter ² =100m²
1 hectare=100m× 100m
= 10000m²
=10⁴m²
1km²= 1km×1km
=1000m×1000m
=10⁶m²
1km²= 100 hectare.
1dm²= 10cm×10cm
=100cm²
=10²cm²
1cm²= 1/100 m × 1/100 m
= 1/10000 m²
= 1/10⁴ m²
=10-⁴ m²
1mm²= 1mm × 1 mm
= 10-⁶ m²
1yard²=0.836m²
1ft²=0.09290 m²
1acre=4046.856m²
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