1.5 scientific investigations

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LESSON 4 - SCIENTIFICINVESTIGATIONS

Inference

Early assessment that is carried out to answerthe questions raised.

The inference should be written as :depend on.OrThe ..changes as the...changes

Hypothesis

A general statement about the relationshipbetween a manipulated variable and aresponding variable.

The hyphotesis should be written as :The greater the, the greater the.OrThe bigger the., the smaller the..

Manupulated variable

The quantity whose values we deliberatelychoose to change or a primary variable whichcauses other secondry variable to change.

Responding variable

The quantity whose value depend on themanipulated variable or a secondry variablewhich changes in response to the change in themanipulated variable.

Fixed variable

The quantity whose value is kept constantthroughout the experiment.

Aim

A statement to show the investigation of thevariables involve.

The aim of the experiment should be written as:To investigate the relationship between..and

Apparatus

List the apparatus and materials used so that atleast a set of data for manipulated and respondingvariables can be determined.

State the arrangement of the apparatus that can

function by drawing a labeling diagram .

Procedure

State the method of controlling the manipulatedvariablesState the method of measuring the respondingvariablesRepeat the experiments at least four times.

Tabulating the data

Record the data in the following table

Manipulated variable Responding variable

Analysing the data

Plot a graph of ( Responding variable) against(Manupulated variable)

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How to tabulate the data ?

The table muast be neatly drawn and the dataarranged in either and rows.The names and symbols of the manipulated andresponding variables must be written together withthe units.For example,

Velocity,v / s

Time , t / s

Volume , V / m3 Pressure , P / Pa

The data shown in the table must be consistent inthe number of decimal places in accordance withthe respective measuring instruments.For example,

Length, l / cm Time , t /s

0 12.8

2 25.6

4 39.4

6 52.28 75.0

If the data too small or too big use the standardform number.

For example

Temperature /oC 10 20 30 40 50

Density, / kgm-3

x 1049.7 8.5 7.3 6.6 5.1

How to plot the graph ?

The title of the graph must be shown.The axes of the graph must be labelled with theunit used.For example:

The scale choosen must be easy to use.Scales such 1:1 , 1:2 , 1:5 ,1:10 ,1:100 arepreffered in plotting a graph.Odd scales such as 1:3 , 1:4 , 1: 6 , 1:7 , 1: 30should be avoided in plotting a graph.

Make sure the area covered by the plotted pointsmust not be less than 50% of the area of the graphpaper.

For example:

The scale on the axes must be uniform and clearlymarked with value.For example:

All the points are marked with a symbol such as across or circle and the centre of the cross mustaccurately positioned.

The best straight line or the best curve graph mustbe drawn.The best straight line or the best curve graph is theline that passes through most of the points plottedsuch that it is balanced by the number of pointsabove and below the line.The line also mustsmooth.

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It is not advisable to plot graph by joining point topoint because the graph obtained is not smooth.

How to analyse the data ?

(a) Determine the relationship between twovariables.Example :

y is directly proportional to x.

or y x

y increases linearly with xor y = mx + cm = gradientc = intercept on axis-y

y decreases linearly with xor y = -mx + cm = gradientc = intercept on axis-y

y is inversely proportional to x

atau y 1

x

(b) Determine the gradient of the graphExample

Draw a sufficiency large triangle to calculatethe gradient of the graph.State the value of gradient with correct unit.The gradient of the graph is

m = y2 - y1x2 - x1

(c) Determine the certain values from the graph.Certain important values can be obtained fromthe graph plotted by drawing a horizontal lineor by extrapolating the graph.

(d) State the precautions should be takenFor example:The circuit connections must be taken off the

switch when taking the reading of theammeters.

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1 Which of the following is the best way totabulate the data ?

A Voltage,V 0 5 10 15 20

Current,I 0 1.7 2.5 3.4 4.2

B Time,t /s 2 4 6 8 10

Density, /

kgm-3

2000 5000 8000 11000 14000

C Period,T/ s

10.5 15.3 19.8 27.9 36.0

Distance,d/m

2.5 3.3 4.6 5.8 6.9

D Objectdistance,u / cm

5.1 8.7 11.6 16.5 18.6

Imagedistance,v / cm

2.3 5 6.9 9 11.6

2 Which of the following scales is the mostsuitable to plot a graph?

A 1 cm : 3 unit B 1 cm : 5 unitC 1 cm : 6 unit D 1 cm : 8.8 unit

3 Which of the following is the best graph ?

4 Which of the following graphs show that yincreases linearly with x?

5 Hookes law states that applied force Fisdirectly proportional to the extensionxofspring if its elastic limit is not exceeded. Whichof the following graphs shows the HookesLaw?

6 The acceleration,a of an object is inversely

proportional to the mass,m of the object

under constant force.Which of the following graphs describes therelationship between a and m .

7 An experiment is carried out to find therelationship between mass and acceleration of

a trolley on a wooden runway.

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The experiment is repeated by adding thenumber of trolleys.The responding variable in this experiment is

A the length of the wooden runway.B accelerationC mass

8 In a simple pendulum experiment, the lengthof the pendulum and time for 20 oscillationsare recorded.The length of the pendulum is a

A manipulated variableB responding variableC fixed variable

9 Based on the graph above, what is the

gradient of the graph?

A - 1.5 B - 0.7C 0.7 D 1.0E 1.5

10 What is the unit of the gradient of the graph

above?

A m B m2 sC ms2 D ms- 2

11 A student plot a graph for a physical quantity ,Q on axis-y against a physical quantity ,R onaxis xThe relationship between Q and R is given byas Q - aR = b ,where a and b are constants.The gradient of vthe graph is

A a B Rb Q

C b D a

12 The resistance R and temperature T for an

electric conductor is given as R = r + aT with

r as the resistance at 0oC dan a as aconstant.A graph of R against T is shown .

What is the resistance ,R of the conductor at a

temperature 60oC ?

A 35 B 47 C 86 D 93

E 180

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The equation of the graph above is

A P = 10Q + 5 B P = 2Q + 10C P = -2Q + 10 D P = 5Q 10

14 The following figure shows a graph U versusV.

Which of the following shows the correctrelationship between U and V?

A U = m V + mn

B U = - m V + mn

C U = m V + nn

D U = - n V + mm

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15 The pressure ,P of the gas is directlyproportional to the absolute temperature, T ofthe gas.When P = 100 ,T = 50. What is the value of Pwhen T = 400.

A 0.8A B 125C 200 D 800E 2000

16 Boyle s law state that the pressure of the gasis inversely proportional to the volume of thegas.The pressure of a buble under sea surface is120 cm Hg Pa and its volume is 15.8 cm3.When the buble rises to the surface of the seathe pressure of the buble is 76 cm Hg.

What is the volume of the buble at the surfaceof the sea?

A 10.0 cm3 B 25.0 cm3

C 124.8 cm3 D 309.1 cm3

E 577.2 cm3

17 An object is released froma height , h and

the time taken to reach the ground is t.2

h/m 20 x

t/s 2 4

If h is directly proportional to t 2 , what is thevalue of x in the table above.

A 10 m B 40 mC 80 m D 160 mE 240 m

18 Newtons universal law of gravitation statesthat the gravitational force of attraction, Fbetween two point masses is inverselyproportional to the square of the distance ,Rbetween them.

If the distance between them is 3R, what isthe gravitational force of attraction ?A 9F B 3FC F D F

3E F

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19 A student carries out an experiment to findout the relationship between the change inlength ,y , of a spring and mass, m , of theload on the spring. The arrangement of theapparatus for the experiment is shown inFigure 1 . The length of the spring when aload is placed on the piston is l.

At the beginning of the experiment there is noload. The length of the spring is lo . The actuallength of lois shownin Figure 2.The experiment is repeated by using load withmass , m , equal to 0.5 kg , 1.0 kg , 1.5 kg ,2.0 kg and 2.5 kg. The actual lengths of thespring when the different masses are used areshown in Figure 3, Figure 4 , Figure 5 ,Figure 6 and Figure 7.

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(a) Based on the aim and the procedure ofthe experiment state the:(i) manipulated variable

________________________________

(ii) responding variable

_________________________________

(iii) constant variable

________________________________

(b) Measure the length of the spring in

Figure 2.lo = ___________________

Measure the lengths l of the spring inFigure 3 , Figure 4 , Figure 5 , Figure 6and Figure 7 when different load areused.

In each case, calculate the change inlength,y, of the spring where;

y= ( lo l)

Tabulate your results for m ,landyin thespace below.

(c) On the graph paper , plot a graph ofyagainst m.

(d) Based on your graph, state therelationship betweenyand m .

_________________________________

_________________________________

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20 40 60 800

l/cm

1

2

3

4

5

T2

/ s2

Graph T2 against l

100

l / cm


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20 A student carries out an experiment toinvestigate the relationship between thelength of a simple oscillating pendulum ,l,with its period, T.The experiment is repeated using differentlengths,l, and their corresponding periods, T,are recorded. A graph of T2 against l, is thenplotted as shown above.(a) Based on the graph,

(i) State the relationship between T2with l.

..

..(ii) Calculate period,T, when the lengthl= 45 cm.(Show your working)

(iii) Calculate the gradient of the graph.

(b) Using the value of the gradient obtainedfrom (a)(iii) and the equation,

calculate the acceleration due to

gravity , g.

(c) State one precaution for this experiment.

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21 The graph above represents graph Wagainst V , where W and V are the distanceson a wooden rod.

(a) Based on the graph state the:

(i) manipulated variable

________________________________

(ii) responding variable

_________________________________

(b) Calculate the gradient of the graph.

(c) Determine the intercept on

(i) axis- W

....................................................

(ii) axis-V

.....................................................

(d) State the equation of the line

...............................................................

22 Pak Abu has a pendulum clock as shown inthe diagram below.

Every day it was observed that the clock wasslow about 2 minutes.Pak Ali raised the position of the bob tocorrect the clock.Based on the observations:(a) State one suitable inference that can be

made.(b) State one appropriate hypothesis for an

investigation.(c) With the use of apparatus such as

pendulum bob , string and otherapparatus, describe an experimental

framework to test your hyphothesis.In your description, state clearly thefollowing:(i) Aim of the experiment(ii) Variables in the experiment(iii) List of apparatus and materials(iv) Arrangement of the apparatus(v) The procedure of the experiment

which include the method ofcontrolling the manipulated variableand the method of measuring theresponding variable

(vi) Way you would tabulate the data(vii) Way you would analysis the data

1.5 scientific investigations

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