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m easurement. By M iss Buicke. What we must know from the syllabus. OP1 Measure length, mass, time and temperature (SI units). Perform simple calculations based on these to find the derived quantities: area and volume. Understand that units of measurement follow the SI system.
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measurement By Miss Buicke
What we must know from the syllabus OP1 Measure length, mass, time and temperature (SI units). Perform simple calculations based on these to find the derived quantities: area and volume. Understand that units of measurement follow the SI system. OP2 Measure mass and volume of a variety of solids and liquids.
Physics is the science of exact measurement of quanties such as length, mass, time, temperature, area and volume. There are lots of different units used for measurement. Can we think of any? Scientists use units called S.I. Units to measure quanties. It is important that S.I units are used. Scientiest all over the world use the same unit of measurement to avoid confusion. S.I. stands for Système International d'unités. itis in french because it was the French who first promoted this system.
A measuring tape in used to measure length A trundle wheel is used to measure the length of large Distances.
An opisometer is used to measure the length of a curved line. A balance is used to measure mass
A graduated cylinder is used to measure volume. A stop watch is used to measure time
A verniercallipers is used to measure the diameter of objects. A thermometer is used to measure temperature
Measuring length. • The SI unit for length is the metre. But length can also be • measured in: • Millimetres(mm) • Centimetres (cm) • Kilometres (km) • Depending on what we are measuring we use the most • appropriate unit. • For example: • when measuring the length of your science copy • we use centimeters.
When measuring the length of the school yard we use meters When measuring the driving distance between Dublin and Kerry we use kilometers. When measuring the thickness of a coin we use millimeters. Remember: 10 mm is the same as 1 cm 100 cm is the same as 1m 1000m is the same as 1 km
Quick check: What could we use to measure the length of a football field? What could we use to measure the thickness of a key? What could we use to measure the length of our desks? What could we use to measure the height of a student? What could be use to measure the length of a stream on a map?
Sample question 1: Convert 8.6 cm to mm 1cm = 10 mm 8.6 cm = 86 mm We multiply 8.6 by 10 .ie 8.6cm x 10 = 86mm Sample question 2: convert 67 mm to cm 10 mm = 1 cm We divide 67 mm by 10 ie. 67mm ÷ 10 = 6.7 cm
Sample question 3: convert 90cm to meters There are 100cm in 1m 10cm = .1 m 90cm = .9m Sample question 4: convert 80 mm to meters Sometimes its easier to work in cm, so we convert 80mm to cm first. 10mm = 1cm 80mm =8cm Now we know that 100cm = 1m so, 1cm = .01 m therefore .01 x 8 = .08 m
Extra questions: Covert 70 mm to cm Answer = 7 cm Covert 4.5 mm to cm Answer = .45 cm Covert 72 cm to mm Answer = 720 mm Covert 83 cm to m Answer = .83 m
Covert 100 mm to m Answer = .1m Covert 80m to cm Answer = 8000cm
Measuring mass: Mass is the amount of matter an object contains Mass is measured in grams (g) or kilograms (kg). Small quantities such as the mass of a chemical you would use in an experiment are measured in grams. The kilogram is more suitable for the mass of a person or the mass of a large bag of potatoes. I kg = 1000 g
It is important to understand the difference between the words mass and weight. In everyday usage, these words often have the same meaning. In physics, they have a very different meaning. The weight of an object is the pull of the earth on it. (we will learn about weight later on) The mass of an object is the amount of matter in it. For now just remember that weight and mass have different meanings in science.
Sample question 5: convert 500 g to kg 1000g = 1kg 1g= .001 kg 500g x .001 = .5 kg Sample question 6: convert .8kg to g 1kg = 1000g .8kg x 1000 = 800g
Measuring time Time is measured using many units, for example the second, the minute, the day, the week, the month and the year. The SI unit for time is the second (s) How many seconds are there in a day? There are 24 hours in a day. Each hour has 60 minutes and each minute has 60 seconds. 24 x 60 x 60 = 86,400 seconds
Measuring area The amount of surface that covers an object is called its area. The unit for area is the centimetre Squared (cm2) or the Metre squared (m2). Area of a rectangle = length x width Area of a triangle = ½ base length x perpendicular height Area of a circle = πr2
Measuring volume Volume = How much space an object takes up The unit for volume is the centimetre cubed (cm3) or the metre cubed (m3). We must be able to calculate the volume of a regular and an irregular object.
Regular shape: Calculate the volume of this box: Formula = length x width x height Length = 6cm, width = 6cm and height = 6cm 6cm x 6cm x 6cm = 216cm3
To find the mass and volume of an irregularly-shaped small stone To find the mass - weigh it on an electronic balance. To find the volume: Drop the stone into a graduated cylinder containing water of a know volume and note the new volume. To get the volume of the stone simply subtract the two readings. In this case the volume = 90cm3– 75cm3= 15 cm3.
