Chapter 2: Measurements in Physics

Keywords

• density
• derived quantities
• estimating floating
• fundamental/basic quantities
• measuring ocean currents
• purity
• relative density
• scientific method
• significant figures
• sinking SI units

By the end of this chapter, you will be able to:

a) understand how to estimate and measure physical quantities: length, area, volume, mass and time.

b) explain how to choose and use the right measuring instruments and select the right units ensuring accuracy of measurement.

c) appreciate that the accuracy of measurements may be improved by making several measurements and taking an average value.

d) identify the potential sources of error in measurement and devise strategies to minimise them.

e) understand the scientific method and explain the steps used in relation to the study of Physics.

f) know that practical investigations involve a fair test analysis, prediction and justification of results, and observations, and apply learning in practice.

g) record data in groups and charts and look for trends.

h) understand and be able to use scientific notation and significant figures.

i) understand density and its application to floating and sinking.

j) determine densities of substances and relate them to purity.

k) understand the global nature of ocean currents and how they are driven by changes in water density and temperature.

2.1: Introduction

Measurements are one of the fundamental concepts in science and generally in real life. Modern society, mostly in the 21st century, simply could not exist without measurement which permeates every aspect of human life. It is only when measurement tools are unavailable that we begin to appreciate just how important they are.

In this chapter, you will learn how to estimate and measure length, area, volume, mass, density and time and express them using appropriate units.

2.2: Estimation and Measurement

The word “measurement” comes from the Greek word “metron”, which means “limited proportion”. Measurement is a technique in which the properties of an object are determined by comparing them to a standard. Measurements require tools and provide scientists with a quantity. A good example of measurement is using a ruler to find length, width or height. In general, scientists use a system of measurement still commonly referred to as the “metric system”. The metric system was first developed in France in the 1790s. Before that time, people used a variety of measurement systems.

This system is called Système Internationalé d’ Unites (French for International System of Units), abbreviated as SI.

Physics is a practical science, based on the measurement of physical quantities. These are some of the questions we normally ask ourselves: How heavy is he? How tall is she? What are the dimensions of the land? We ask so many such questions.

Estimate means using prior experience and sound physical reasoning to state a rough idea of a quantity’s value, like he is about 70 kilogrammes, there are about 4 centimetres, this chicken has a heavy weight.

Estimation is a skill one should have. There are commonly used skills like estimating one metre to a stretch, the width of your palm is estimated to be 10 centimetres etc.

Can you now mention other situations where people use estimation in daily life?

You, too, can develop the skill of producing reliable estimates of lengths, weights, volumes, heights and so many other things. How?

When you need an approximate idea of length, you have a handy “ruler” always nearby your body.

Yes, your body and its various parts – can serve as a quick length estimator. For example, for an average man or woman:

DID YOU KNOW

1. The hand: The width of the palm is about 10 centimetres.
2. The foot: An average foot is about 30 centimetres long.
3. The forearm from elbow to fingertip: Your forearm is about 46 centimetres.
4. From nose to finger tip: The distance between the nose and the fingertip when the arm is extended is about 90 centimetres. If you have not heard of this method yourself, ask your mother or grandmother; it was the traditional way of measuring cloth.
5. The distance of one full stride: Called a pace, it is about 145 centimetres for an average man or woman. The Romans used this measurement.

Activity 2.1 Using different devices to measure

Key Question: In your groups, discuss different devices used for measurement of quantities.

What you need

Textbooks and the internet.

What to do

1. In groups, discuss about the accurate use of the following instruments: Tape measures, rulers, vernier calipers, stop watches/clocks, balances, measuring cylinders and displacement cans.

2. Which quantity is each instrument stated above used to measure and in which units?

3. Share your group’s findings in class.

Activity 2.2 Estimating lengths and heights

Key Question: How to estimate length and heights.

What you need A ruler, four books of different sizes, and a tape measure.

What to do In groups, use the ruler to find out how wide your palm is and how long your forearm is.

1. Do not place your forearm on anyone but use its length to estimate the height of your friend that is seated next to you.

2. Estimate the length and width of each of the books based on the width of your palm. Do not place your palm on any book! Record what you get in each case.

3. Using the tape measure, accurately measure the height of your friend seated next to you.

4. Compare the results of your estimates of the height and the length you attained after using a tape measure.

5. Share your findings with classmates.

Questions

a) Why do you think there are differences between the estimates and the actual heights obtained?

b) What do you think could have caused this difference?

c) How can we improve the reliability of an estimate?

2.3: Scientific Measurements

To be sure, accurate measurements of physical quantities have to be carried out.

A physical quantity is a property of a material that can be quantified by measurement like length, mass and time.

We can achieve accurate measurement by use of the different instruments available in a Physics laboratory.

Do you recall some of the instruments?

Measurements of physical quantities are always expressed in terms of units, which are standardised values. For example, the length of a race, which is a physical quantity, can be expressed in units of metres (for short length) or kilometres (for long lengths). Without standardised units, it would be extremely difficult for scientists to express and compare measured values in a meaningful way.

A physical quantity can be expressed as the combination of a magnitude and a unit. These quantities are divided into two:

1. Derived quantities of measurement: These are quantities that are expressed from two or more quantities. They cannot be measured directly.

2. Fundamental quantities of measurement: These are independent physical quantities that are not possible to express in other physical quantities. They are measured directly using specific instruments.

These quantities are summarised in the table below:

2.4: Measurement of Length

When a person says that I have drawn a line which is 15 cm long, what does he/she mean? 15cm means the length of the line.

Length is a measure of distance. The SI unit for length is metre. We can measure length using a number of tools. Can you name some tools?

Activity 2.3 Measuring and estimating the height of a learner

What you need A metre rule and tape measure.

What to do Observe the figures below and answer the questions that follow.

Figure 2.1: Measuring height

1. Explain the case in which the teacher will be able to get the exact height of the learner.
2. In pairs, practise the above demonstration and state your observations in both cases.

Activity 2.4 Measuring different lengths

Key Question: How can you measure different physical quantities?

What you need Tape measure, metre rule, vernier calliper and stop clock.

What to do

In groups, estimate, measure and state the appropriate units of measurement in each case.

1. Length of the football pitch.

2. The area of a desktop.

3. The width of a classroom.

4. The thickness of a desktop.

5. The time a friend takes to walk 20 paces.

6. Compare the measured and estimated value.

Note down your findings and present your group’s findings to the whole class.

Activity 2.5 Comparing measurements obtained by different instruments

Key Question: How can you compare measurements obtained from different instruments?

What you need A metre ruler or tape measure, vernier callipers and micrometre screw gauge, a book.

Figure: Instruments used to measure length

1.(a) Measure the thinkness of a book using a micrometre screw guage and a vernier callipers.

(b) Measure the length of a classroom using a metre rule and a tape measure.

Compare the values of the measurements obtained in (a) and then in (b) above.

3. Basing on your understanding, what can be best used to measure:

a) the thickness of a book?

b) the length of a classroom?

Conversion of units of length

Different instruments are calibrated or marked in different units. For instance, we do not measure the length of a pencil using a ruler in metres but in centimetres. In such a case, one has to convert kilometre (km) to centimetre (cm).

Generally, the conversion of one unit to another unit of the same quantity is performed using multiplicative conversion factors. Let us see how to convert different units of length and mass. Conversions can be made basing on the figure below:

Figure 2.3: Conversions of length

EXERCISE 2.1

Convert the following measurements to the units indicated:000

a) 7 cm to mm.

b) 8 m to cm.

c) 9 km to m.

d) 12.4 km into metres.

e) 0.56 m into millimetres.

f) 0.45 mm into metres.

g) 3.04 km into centimetres.

h) 21.4 cm into millimetres.

2.5: Measurement of Area

Area is a quantity representing the amount or extent of surfaces. It is usually measured or defined on a flat surface or a spherical surface.

The standard unit of area in the International System of Units (SI) is the metre squared (m2). In science, we compare the surfaces by determining a property of the objects in question called area.

Every solid has an area, including you! Areas of regular shapes like triangle and rectangle can be determined by use of formulas, while area of irregular solids is determined using other methods. To determine the area of either a rectangular or square surface, we need to measure its width (breadth) and its length.

The product of the width and length is what we call area. In case dimensions of width and length are expressed in different units, care must be taken to change into metres.

For example:

1 m = 100 cm ⇒ (1 m)2 = (100 cm)21 m2 = 10,000 cm2

Similarly;

1 m = 1000 mm → (1 m)2 = (1000 mm)2 →1 m2

= 1,000,000 mm2

Activity 2.6 Measuring of area

Key Question: How can you measure area?

What you need A metre ruler and tape measure.

What to do

In groups, use the materials provided to measure the width and the length of:

1. The desk tops in the laboratory.

2. The floor of the laboratory.

3. The blackboard of the laboratory.

4. Your Physics exercise books.

2.6 Measurement of Mass

Mass is a measure of how much matter is in an object. Therefore, in whatever we do we need to know the mass of an object to determine its weight and the amount of force required to move it.

For example, if you want to lift a heavy box, you need to know its mass so that you can determine how much force you need to apply to lift it.

Density is calculated by dividing the mass of an object by its volume. The formula for density is:

Density = Mass / Volume

The unit for density is kg/m³. For example, if an object has a mass of 10 kg and a volume of 2 m³, then its density is 5 kg/m³.

Excersice 2.2

You can measure the length of your room using a tape measure and then calculate its area by multiplying the length by the width. You can also measure the mass of an object using a weighing scale and then calculate its density by dividing the mass by its volume.

Activity 2.7 Comparing instruments for measuring mass

Figure 2.4: Instruments used to measure mass

Observe the pictures above and answer the questions that follow:

1.What specific name can you assign to the instruments shown above?

2.What are the instruments used for?

3.Of the two instruments, which one would you recommend for measuring the mass of:

(i) sugar (ii) posho (iii) meat (iv) potatoes

Explain your reasoning in each case.

4. What is the equivalent of a kilogram in grams?

Mass and weight

As earlier discussed, mass is the amount of matter an object contains and weight refers to the measurement of the pull of gravity on an object. Mass becomes weight when an object being measured is suspended and acted upon by the force of gravity. The force of gravity is the force with which the earth pulls objects to itself.

We calculate weight from w = mg

Where w = weight

m = mass of an object

g = acceleration due to gravity

On earth’s surface, g = 10ms-2

Assignment 2.1 Measuring of mass

What you need Spring balance, beam balance and a stone (of relatively small size)

What to do

a) Visit your laboratory and have a spring balance and a beam balance.

b) Weigh the stone using a beam balance, read and record your observations

c) Then weigh the same stone using the spring balance and record your observations.

d) How are the obtained results related? Share your findings with the rest of the class.

Comparison Chart

Table 2.3: Comparison between mass and weight

2.7: Measurement of Volume

Activity 2.8 Measuring volume of a liquid

What you need

A beaker (container), liquid, e.g. water

What to do

(i) Pour water in a beaker

(ii) Read and record on the side of a beaker where water reached

(iii) Add more water.

Question

1. What did you observe?

2. What is the first value and second value as read from the scale of the beaker?

The SI unit for volume is cubic metres (m3). However, we can also measure water in centimetres cubed (cm3) and litres (4).

That is,

1 m = 1000 mm

1 m3 =1000 litres

2.8 Volume of a Regular Solid

From our earlier observations, there are two types of objects, namely regular objects and irregular objects. Since the shapes of these two types of solids are different, we must also use different methods of measurement to determine their volumes.

Let us begin with regular shaped objects such as boxes, desks and many more.

A very good example of a regular shaped object is the cuboid below.

Figure 2.5: A cuboid

The volume of a cuboid is calculated from the expression :V = lxWxh

Example 2.1

Find the volume of the cuboid in the diagram below:

What to do

1. Work in pairs and measure the width, length and height of the wooden block and empty box provided using the measuring instruments shown.

2. Record all your measurements.

3. Meseasure the diameter of the ball using the metre rule.

4. Determine the volume of each of the objects that you have measured.

5. Compare the volume you have obtained with a metre rule to the volumes determined by tape measure. Are they the same or not?

6. If not, what do you think causes the values to be different, yet you all measured the same object?

2.9: Volume of an Irregular Solid

Irregular solids are those whose shapes are not defined like stones, beams etc.

Can you apply your tape measure or metre rule and then accurately determine the volume of such erregular objects? No! And yet sometimes we need to accurately determine the volume of an irregular solid. We use a method that scientists call the displacement method, where we use water and a calibrated beaker.

Activity 2.10 Measuring volume of irregular solids

Key Question: How can you measure the volume of an irregular solid?

What you need

An overflow can, a measuring cylinder or a 100 ml beaker, 1 metre long piece of thread, a 1 litre (or 2 litre) jugful of water, metallic soda bottle tops, and a small stone.

What to do In groups, conduct the following experiments:

Experiment 1

1. Completely, fill the overflow can with water so that some of the water overflows through the spout. Wait until the water stops dripping from the overflow can.
2. Place the measuring cylinder or a 100 ml beaker under the spout(s) of the overflow can.
3. Tie a bottletop using the thread provided and gently lower it into the full overflow can till it is completely covered by the water (submerged in water).
4. Carefully, collect all the water dripping out of the spout of the overflow can till the dripping stops.
5. Determine the volume of water collected in the beaker.
6. Repeat this for all the remaining woled hisdo bottletops and record the results in a suitable table. Determine the average value.

Experiment 2

1. Completely fill the overflow can with water so that some of the ed nac water overflows. Wait until the water stops dripping from the overflow can.
2. Place the 100 ml beaker under the spout of the overflow can.
3. Tie the stone using the thread provided and gently lower it into the full overflow can till it is completely covered by the water (submerged in water).
4. Carefully collect all the water dripping out of the spout of the overflow can till the dripping stops.
5. Determine the volume of water displaced from the scale of the beaker.

NB: The volume of the displaced water is the volume of the stone that was submerged in water.

Experiment 3

1. Pour water in a measuring cylinder to about half of its scale.
2. Record the volume of water from the scale as V,.
3. Tie the stone using the thread provided and gently lower it into the measuring cylinder till it is completely covered by the water.
4. Record the new volume of water from the scale as v2.
5. Determine the volume, v,, of the stone from the expression V=V2-V1

Conversion of units of volume

It is always necessary to change the units of measurement of volume depending on what we want to measure. We can use the chart below to understand how conversions of liquids can be done:

EXERCISE 2.3

Convert each of the following measurements into the unit shown in brackets.

a) 3.51 (ml) b) 2300 mm3 (cm3) c) 5.4 m3 (1)

Volume of a liquid

Aunt Sikola Namatovu loves to take milk at breakfast time. She goes to buy it herself but sometimes she sends her niece, Sauda Nakato. At the fresh milk centre, the milkman measures out milk using a particular container and pours the milk into the jug normally used for buying milk. The milkman always uses that particular container for measuring out milk for his other customers. He charges them according to the number of containers full of his milk that he has given to a customer.

Figure 2.6: A man pouring milk into a container

To measure out the volumes of the liquid, we have to use a particular containers that are specially designed to accurately determine the volume of the liquid in question. The special measuring container has a particular capacity of liquid it can measure out. The milkman is using a specially designed container for measuring out milk in a particular unit. Have you ever seen the containers in Figure 2.6? What is the volume of milk that they can contain?

In the laboratory, we sometimes find ourselves measuring small volumes of liquids, such as water and oil, among others. In such cases, we use containers with smaller volumes to measure the volumes of these laboratory liquids. These containers have smaller units like cubic centimetres (cm3) and millilitres (ml).

Figure 2.7: Materials used for measuring the volume of liquids

NOTE:

While measuring the volume of liquids like milk, oil and water, you need to get down and look from the same level as the liquid itself. You need to look directly at the meniscus, as seen in Figure 2.8 below:

Figure 2.8: Correct reading of the meniscus of a measuring cylinder

Activity 2.12 Measuring volume of liquids

Key Question: How can one measure the volume of liquids?

What you need A 100 ml measuring cylinder, a 50ml measuring cylinder, a 50ml conical flask, a 10ml measuring cylinder, a 100ml beaker, a jugful of water and a 500ml plastic soda bottle top.

What to do

In groups, follow the set instructions below:

NOTE: Make sure you do not spill water on your books and table.

1. Carefully, fill the bottle top with water and pour this water into the empty beaker that you have been provided. Do this again until you have poured out four (04) bottle top-full of water into the beaker.

2. Measure the volume of the water in the beaker using:

a) 100ml measuring cylinder

b) 50ml measuring cylinder

c)10ml measuring cylinder

3. All group members should attempt to read off the volume of water in each case.

4. Discuss and agree on a particular value of the volume to be recorded. Note down all the readings.

5. Fill the conical flask completely with water.

6. Measure the volume of the water in the conical flask using:

100 ml measuring cylinder

Questions

a) In the first experiment, compare the values you obtained from the volume of water of four bottle tops for the different measuring cylinders. For which cylinder do you believe you got the accurate volume? Why do you believe this?

b) In the second experiment, which measuring cylinder gave you the more accurate results?

c) Compare your findings with those of the other groups and discuss the differences.

2.10: Meaning of Density

Look at the items in the figure below. Can you easily tell which one of them is the heaviest? Enead

Figure 2.9: Different objects

In Physics, we can easily tell the weight of something if we know its property called density.

The density of a material is defined as its mass per unit volume. This is usually abbreviated as Thus, we can write p = m where V’ p is density, m is mass and V is volume of the same object.

The SI unit of density is the kilograme per cubic metre (kgm3). Another unit of density is grams per cubic centimetre (gcm3).

DID YOU KNOW

1gm3 = 1000m-3

EXAMPLE 2.2

Calculate the density of the brick below, assuming it has a mass of 150 g.

2.11: Density and its Application in Sinking and Floating

Activity 2.13 Comparing densities

What you need A stone, water, a beaker, a pencil or pen.

What to do (i) Pour water in a beaker to about half. (ii) Gently place a stone and pencil in water. (iii) What do you observe?

Question

1. In groups, explain yoour observations in (iii) above.

2. Carry out other investigations of densities of different items with water.

Ice floats on water because the density of ice is less than the density of water.

Aluminium sinks because its density is greater than the density of water.

Figure 2.10: Comparison of densities with water

What conclusion can you draw from your observations in Figure 2.10?

NOTE: Water has the highest density at 4°C.

Density of water and ocean currents

Fluctuations in both temperature and salt content lead to different regions of ocean water having different densities. Higher temperatures, such as near the equators, cause a given mass of water to expand and therefore drop in density. Also, lower salt content causes a given mass of water to be lower in density. Gravity causes the denser water to fall, pushing away the less dense water, which shoots sideways and rises. Giant convection loops of ocean currents form as the lighter (hotter, less salty) regions of water rise and flow to replace the heavier (colder, saltier) regions of water. The effect of density-driven currents is fundamentally a result of the interplay between heating from the sun, earth’s gravity, and salinity differences.

Assignment 2.2 Researching on densities of water of ocean currents

In groups, make a comprehensive research on the following:

a) How ocean currents are related to the changes in density.

b) The possible impact on ocean currents on the warming of the North Atlantic due to climate changes.

2.12: Density and Relative Density

Relative density is defined as the ratio of density of a particular substance to the density of water.

Relative density has no units of measurement. Can you explain why?

When the relative density of a substance is less than 1,then, it is less dense than water and the reverse is true. But when the relative density is exactly equal to 1, then, the density of the material is equal to that of water.

Exercise 2.4

Refer to Figure 2.10.

Determine the relative density of cork, ice, aluminium and lead

What is the relation between relative density and floating or sinking?

EXERCISE 2.5

Explain why coins sink in water.

A boat is heavier than a 500 coin.

2.13: Density and Purity

It is possible to determine the purity of a substance using its density. Take the example of gold with a density of about 19.3 gcm-3. In case you find that after determining its density, it is different from this expected value, then know that the sample you used is impure (not pure).

2.14: Measurement of Time

Ever since man first noticed the regular movement of the Earth and other stars, people have wondered about the passage of time. Recording time has been a way by which human beings have observed the heavens and represented the progress of civilisation.

During the passage of time, there were many other events that indicated significant changes in the environment. Dry seasons and rainy seasons, the flowering of trees and plants, and the breeding cycles or migration of animals and birds, were all used as measurements of time.

But they could not measure short intervals of time during daytime or at night! Ancient Italians developed a machine to measure time. This machine is called a pendulum.

In our villages, our people tell the time of the day by noting the crowing of a cock. Sometimes, they use the position of the sun in the sky or the shadows to tell the time of the day!

The following are some of questions one should ask: Measurements in Physics

a) Can you use a cock or the position of the sun in the sky to time how fast Michael Mubiru is in the 100-metre race?

b) Can you use a pendulum to measure how fast Miriam Mbabazi can run the 400-metre race?

NO! You need something better to help you measure time in a given event. And that something is a clock or watch.

In the Physics laboratory, we use special clocks called stop clocks and stop watches to help us to measure different time intervals in different experiments. Below are pictures of the clocks and watches that we use to measure time.

Activity 2.14 Measuring time

Key Question: How is time measured?

What you need

A stop clock, a 1.5-metre-long piece of thread (or fine string), a retort stand and a pendulum bob.

What to do

In groups, perform this activity:

1. Carefully, tie a bob at one end of your string.

2. Clamp the other end of the string onto the retort stand so that the length that is hanging is exactly 1 metre.

3. Displace the bob slightly to the side and then allow it to swing. Using your stop clock, measure and record the time in seconds that is taken by your pendulum to make:

• 5 swings
• 10 swings
• 15 swings
• 20 swings
• 25 swings

4. In each experiment, determine the time taken by the pendulum to make one (1) swing by dividing the total time taken by the swings by the number of swings.

5. Tabulate your results in a suitable table.

6. Compare your results with your classmates.

Question

What are the likely sources of errors in this experiment?

2.15: Accuracy in Measurements

Measurement is the foundation of all experimental sciences and technology. The result of every measurement by any measuring instrument contains some uncertainty. This uncertainty is called error.

When you buy some meat from the butcher, sometimes the mass of meat they bring back home will not be exactly what you had asked for. Most times it is less because of how the butcher weighs it.

NOTE:

What do you think causes the mass of the meat to be less?

This difference between what you asked for and what was given by the butcher is an error.

In carrying out measurements, there are two things that we have to think about. We have to think about the accuracy of our measurement and about the precision of our measurement.

Therefore, accuracy refers to the closeness of a measurement to the true value of the physical quantity, and precision refers to the resolution or the limit to which the quantity is measured.

In other words, the accuracy of a measurement is a measure of how close the measured value is to the true value of the quantity, and precision tells us to what limit the quantity is measured.

2.16: Significant Figures

In this section, we are going to learn about what scientists call “significant figures” and what they term as “rounding off”.

We shall also learn about something called “scientific notation”. This is very important when you are reporting the results of your measurements in the different experiments you will be doing.

It is important to be honest when reporting a measurement so that it does not appear to be more accurate than the equipment used to make the measurement errors. We can achieve this by controlling the number of digits, or significant figures, used to report the measurement.

Rules for counting significant figures are summarised below:

a) Zeros within a number are always significant. Both 7208 and 20.09 contain four significant figures.

b) Zeros that do nothing but set the decimal point are not significant. Thus, 470,000 has two significant figures.

c) Trailing zeros that are not needed to hold the decimal point are significant. For example, 4.00 has three significant figures.

d) Non-zero digits are always significant.

e) Any zeros between two significant digits are significant. A final zero or trailing zeros in the decimal portion ONLY are significant

NOTE:

As we improve the sensitivity of the equipment used to make a measurement, the number of significant figures increases.

For example:

Spring balance 3 gm accuracy to 1 gm 1 significant figure

Beam balance 2.53 gm accuracy to 0.01 gm 3 significant figures

Electronic balance 2.531 gm accuracy to 0.001 gm 4 significant figures

The significant figures (sometimes known as the significant digits and decimal places) of a number are digits that carry the meaning of the measurement and thus contributing measurement resolution.

EXAMPLE 2.3

If A = 334.5 kg and B = 23.43 kg then,

A + B = 334.5 kg + 23.43 kg= 357.93 kg

The result with significant figures is 357.9 kg

In other words, when carrying out a multiplication or division, the result should be reported to the same number of significant figures as that of the number with a minimum of significant figures. However, for addition and subtraction, the results should be written with the smallest number of decimal places of the numbers being added or substracted.

EXERCISE 2.6 Work out the following:

i) 0.04 x 0.452

ii) 90.12/ 2.01

Rounding Off

When the answer to a calculation contains too many significant figures, it must be rounded off.

There are 10 digits that can appear in the last decimal place in a calculation. One way of rounding off involves underestimating the answer for five of these digits (0, 1, 2, 3, and 4) and overestimating the answer for the other five (5, 6, 7, 8, and 9).

Activity 2.15 Finding out more about scientific notation

State the significant figures in each of the following figures: But othe For

(i) 2.4 x 1022 (ii) 9.80 x 10-4 anim (iii) 1.055 x 10-22

Commonly used prefixes and abbreviations for numbers in scientific notation are shown in Table 2.4 below:

The scientific method in studying Physics

The scientific method is a process for gathering and refining data, information and knowledge. The scientific method is a process for all scientists to carry out experiments that are used to explore observations in experiments and then to answer questions.

But there are some areas of science that are more easily tested than others.

For example, scientists studying how stars change as they age or how animals digested their food during their lifetime, hundreds of years ago, cannot fast-forward a star’s life by a million years or run medical examinations on feeding animals to test their hypotheses.

When direct experimentation is not possible, scientists modify the scientific method.

But even when modified, the goal remains the same: to discover the cause and effect relationships by asking questions, carefully gathering and examining the evidence, and seeing if all the available information can be combined into a logical answer.

Even though the scientific method is a series of steps, keep in mind that new information or thinking might cause a scientist to back up and repeat steps at any point during the process.

Whether you are doing a science class project, a classroom science group activity, independent research, or any other hands-on science inquiry, understanding the steps of the scientific method will help you to focus your scientific question and work through your observations and the data obtained, to answer the question as well as possible.

Steps of the scientific method

The steps of the scientific method are as follows:

Assignment 2.3 Researching on the steps of the scientific method in studying Physics

What to use: Internet, textbook

a) In groups, find out the necessary steps required for the scientific method.

b) Write short notes on each of the steps.

c) Present your work to the rest of the class.

Research on the project given to you by your teacher, following the above steps.

Activity 2.16 Comparing the rate of cooling of water

In groups, apply the steps involved in the scientific methods to determine the cooling rate of water.

a) Predict materials you can use to compare the rate of cooling of water and discuss how such an experiment can be conducted in the laboratory.

b) What do you think are some of the variables that should be measured? Also, how often can you repeat your experiment to obtain reliable results?

c) Discuss how best you would present the obtained results or recordings. Also, explain any method you can use to interpret the results.

d) Discuss any methods that you know that one can use to make an analysis of results and to draw conclusions.

e) Do you think there is a possibility of having errors in reading, recording or tabulating your results? Discuss all that you think can be sources of errors.

f) Suggest any improvement one can do to limit errors while performing a scientific experiment. Share your group’s findings in class.

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