1.5 analysing scientific investigations

1.51.5ANALYSING SCIENTIFIC ANALYSING SCIENTIFIC

INVESTIGATIONINVESTIGATION

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Chapter 1 Chapter 1 Introduction To PhysicsIntroduction To Physics

Learning OutcomesLearning Outcomes

IdentifyIdentify variables variables in a given situation in a given situationIdentify a Identify a questionquestion suitable for suitable for scientific investigationscientific investigationForm a Form a hypothesishypothesisDesign & carry outDesign & carry out a simple a simple experimentexperiment to test the hypothesis to test the hypothesisRecord & present dataRecord & present data in a suitable in a suitable formformInterpret dataInterpret data to draw a to draw a conclusionconclusionWrite reportWrite report of the investigation of the investigation


Steps In A Scientific InvestigationSteps In A Scientific Investigation

1.1. Making observationsMaking observations

2.2. Drawing inferencesDrawing inferences

3.3. Identifying and controlling Identifying and controlling variablesvariables

4.4. Formulating a hypothesisFormulating a hypothesis

5.5. Conducting experimentsConducting experiments


1. Making observations1. Making observations

Making observations and gathering Making observations and gathering all available all available informationinformation about the about the objectobject or or phenomenonphenomenon to be to be studied.studied.

Observations are made using the Observations are made using the senses of senses of sight, hearing, touch, sight, hearing, touch, taste, taste, and and smellsmell..


2. Drawing inferences2. Drawing inferences

An inference is a An inference is a conclusionconclusion that that you draw from an you draw from an observationobservation or or eventevent using using informationinformation that you that you already have on it.already have on it.


3. Variables3. Variables

Variables are factors or physical Variables are factors or physical quantities which change in a scientific quantities which change in a scientific investigation.investigation.

3 types of variable:3 types of variable:

1. Manipulated Variables (MV) 1. Manipulated Variables (MV)

2. Responding Variables (RV)2. Responding Variables (RV)

3. Constant/Fixed Variables3. Constant/Fixed Variableswww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

Manipulated VariablesManipulated Variables

Manipulated variables are Manipulated variables are physical quantities which you physical quantities which you control and changecontrol and change for the for the purpose of investigating the purpose of investigating the results of an experiment.results of an experiment.


Responding VariablesResponding Variables

Responding variables are physical Responding variables are physical quantities which are the quantities which are the resultresult of the of the changes madechanges made to the to the manipulatedmanipulated variables.variables.

Affected by the manipulated variable Affected by the manipulated variable & is measured experimentally& is measured experimentally


Constant/Fixed VariablesConstant/Fixed Variables

Constant variables are physical Constant variables are physical quantities which are quantities which are kept constantkept constant during the experiment.during the experiment.

Does not change in the Does not change in the experimentexperiment


4. Hypothesis4. HypothesisA hypothesis is a A hypothesis is a statementstatement of of relationshiprelationship between the between the manipulated manipulated variable variable andand the responding variable the responding variable we would expect in the phenomenon we would expect in the phenomenon under investigation.under investigation.

Can either be true or falseCan either be true or false

must be tested to verify its validity must be tested to verify its validity

The test is in the form of experiments.The test is in the form of experiments.www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

Conducting ExperimentsConducting Experiments

Experiments must be planned and Experiments must be planned and conducted to test a hypothesis.conducted to test a hypothesis.

The conducting of an experiment The conducting of an experiment includes the compilation and includes the compilation and interpretation of data until a interpretation of data until a conclusion can be made regarding conclusion can be made regarding the validity of the hypothesis.the validity of the hypothesis.


ResultResult

Tabulate data Tabulate data

Systematic Data TableSystematic Data Table



t t t



t t t

Name,Symbol/unit

RV

MVSecondary

data

Consistent no. of d.p.www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

Rules No. 1Rules No. 1

The row at the top of the table must The row at the top of the table must contain the name of the contain the name of the

a) variable a) variable

b) symbolb) symbol

c) unit of measurement.c) unit of measurement.



Manipulated variables are filled in the Manipulated variables are filled in the first column.first column.

The values are fixed at uniform The values are fixed at uniform intervals such as 10 cm, 20cm, 30 cm, intervals such as 10 cm, 20cm, 30 cm, and soon.and soon.

The values must also be in ascending The values must also be in ascending or descending order. or descending order. *Avoid recording readings haphazardly*Avoid recording readings haphazardly



Responding variables are filled in the second Responding variables are filled in the second column. column.

The values are obtained from measurements The values are obtained from measurements made during the experiment. made during the experiment.

Normally; this column is divided into several Normally; this column is divided into several columns when repeated measurements of the columns when repeated measurements of the responding variable are taken.responding variable are taken.

The average value is calculated and used in the The average value is calculated and used in the calculations.calculations.



All numerical values must be stated to All numerical values must be stated to the same number of decimal places. the same number of decimal places.

Values derived from measured values Values derived from measured values can be expressed to the same can be expressed to the same number or to an additional number of number or to an additional number of decimal places.decimal places.



The third and subsequent columns The third and subsequent columns normally show values that are derived normally show values that are derived from the responding variable. from the responding variable.

These values are used in drawing the These values are used in drawing the graph.graph.


GraphGraph


Graph T againstGraph T against L LPeriod, T/s

Length, L/cm

Scale

T-axis: 1 cm :0.1 s

L-axis: 1 cm : 5 cm



(a)(a) (b)(b)www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

Point A is balanced by point B,Point A is balanced by point B,if the perpendicular distances AX = BYif the perpendicular distances AX = BY


The graph is not a line of best fit although it passes The graph is not a line of best fit although it passes through all the points except one. through all the points except one. The graph is drawn giving equal emphasis to five The graph is drawn giving equal emphasis to five points only, leaving the last point isolated from all points only, leaving the last point isolated from all the other points.the other points.


The graph is a line of The graph is a line of best fitbest fit it gives it gives equal emphasisequal emphasis to all the points to all the points which are evenly spaced out around which are evenly spaced out around the line.the line.


The graph is not a curve of best fit The graph is not a curve of best fit

the points are not equally spaced out around the points are not equally spaced out around the curve. the curve.

The number of points above the curve is not The number of points above the curve is not equal to the number of points below the curve.equal to the number of points below the curve.


The graph is a curve of best fit The graph is a curve of best fit

all the points are equally spaced out around the curve.all the points are equally spaced out around the curve.



Analysing GraphsAnalysing Graphs

The relationship between two variables in a The relationship between two variables in a linear graph can be written as:linear graph can be written as:

y = mx + cy = mx + cwhere where

y = responding variabley = responding variablex = manipulated variablex = manipulated variablem = gradient of graphm = gradient of graphc = intercept on the y-axisc = intercept on the y-axis

The constants m and c can be determined by The constants m and c can be determined by analyzing the graph drawn.analyzing the graph drawn.


Gradient of the graphGradient of the graph

The gradient of the graph, m is defined as The gradient of the graph, m is defined as the ratio of the change in the value y on the ratio of the change in the value y on the y-axis to a change in value x on the the y-axis to a change in value x on the x-axis. x-axis.

The gradient shows the magnitude of the The gradient shows the magnitude of the change in the responding variable to a unit change in the responding variable to a unit change in the manipulated variable.change in the manipulated variable.



4 setia until here 28/14 setia until here 28/1





Determination of the gradient of a Determination of the gradient of a curvecurve



Extrapolating a graphExtrapolating a graphIntrapolatingIntrapolating


Question No. 1(d): Type of GraphQuestion No. 1(d): Type of Graph5 type of graphs:5 type of graphs:

1.1.Directly ProportionalDirectly Proportional

2.2.Inversely ProportionalInversely Proportional

3.3.Increase LinearlyIncrease Linearly

4.4.Decrease LinearlyDecrease Linearly

5.5.Increase, IncreaseIncrease, Increase

1.1.Scale must not be odd scaleScale must not be odd scale

2.2.MV and RV-Axis title by MV and RV-Axis title by

““Name, Symbol/Unit” Name, Symbol/Unit”

4.4.Transfer all the points correctlyTransfer all the points correctly

5.5.Draw the best fit graphDraw the best fit graphwww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

RV is RV is Directly Proportional Directly Proportional to to MVMV

RV

MV0www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

RV is RV is Inversely ProportionalInversely Proportional to MVto MV

RV

MV0www.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com

RV RV Increases LinearlyIncreases Linearly to to MVMV

RV

MV0


RV RV Decreases LinearlyDecreases Linearly to to MVMV

RV

MV0


RV RV IncreasesIncreases as MV as MV IncreasesIncreases

RV

MV0

RV

MV0

or


1.5 analysing scientific investigations

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