7/24/2019 Pearson Baccalaureate Physics SL Chapter1
1/141
1 Physics and physicalmeasurement
Range of magnitudes of quantities in ouruniversePhysics seeks to explain the universe itself, from the very large to the very
small. At the large end, the size of the visible universe is thought to be around
1025m, and the age of the universe some 1018s. The total mass of the universe is
estimated to be 1050kg.
The realm of physics1.1
Assessment statements
1.1.1 State and compare quantities to the nearest order of magnitude.
1.1.2 State the ranges of magnitude of distances, masses and times that
occur in the universe, from the smallest to the largest.
1.1.3 State ratios of quantities as different orders of magnitude.
1.1.4 Estimate approximate values of everyday quantities to one or two
significant figures and/or to the nearest order of magnitude.
How do we know all this is true?
What if there is more than one
universe?
A planet was recently discovered in
the constellation Libra (about 20 light
years from Earth) that has all the right
conditions to support alien life. This
artists impression shows us how it
might look.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
2/142
Physics and physical measurement
Rest mass is the mass of a particle
when at rest; the mass increases ifthe particle moves fast enough.
If we can split an atom why cant
we split an electron?
The diameter of an atom is about 1010m, and of a nucleus 1015m. The smallest
particles may be the quarks, probably less than 1018m in size, but there is a much
smaller fundamental unit of length, called the Planck length, which is around 1035m.
There are good reasons for believing that this is a lower limit for length, and we
accept the speed of light in a vacuum to be an upper limit for speed (3 108ms1).
This enables us to calculate an approximate theoretical lower limit for time:
timedistance
_______
speed
1035m
________
108ms11043s.
If the quarks are truly fundamental, then their mass would give us a lower limit.
Quarks hide themselves inside protons and neutrons so it is not easy to measure
them. Our best guess is that the mass of the lightest quark, called the up quark, is
around 1030kg, and this is also the approximate rest mass of the electron.
You need to be able to state ratios of quantities as differences of orders of magnitude.
For example, the approximate ratio of the diameter of an atom to its nucleus is:
1010m
_______
1015m105
105is known as a difference of five orders of magnitude.
Some physicists think that there are
still undiscovered particles whose
size is around the Planck length.
What are the reasons for there
being a lower limit for length?Why should there be a lower limit
for time?
Production and decay of bottom quarks.
There are six types of quarks calledup,
down, charm, strange, topand bottom.
Figure 1.1 The exact position of
electrons in an atom is uncertain; we
can only say where there is a high
probability of finding them.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
3/143
This is not a small ratio; it means that if the atom were as big as a football pitch,
then the nucleus would be about the size of a pea on the centre circle. This implies
that most of the atoms of all matter consist of entirely empty space.
Another example is that the ratio of the rest mass of the proton to the rest mass of
the electron is of the order:
1.67 1027kg
_____________
9.11 1031kg2 103
You should be able to do these estimations without using a calculator.
You also need to be able to estimate approximate values of everyday quantities to
one or two significant figures.
For example, estimate the answers to the following:
How high is a two-storey house in metres?
What is the diameter of the pupil of your eye?
How many times does your heart beat in an hour when you are relaxed?
What is the weight of an apple in newtons?
What is the mass of the air in your bedroom?
What pressure do you exert on the ground when standing on one foot?
There is help with these estimates at the end of the chapter.
Measurement and uncertainties1.2
Assessment statements
1.2.1 State the fundamental units in the SI system.
1.2.2 Distinguish between fundamental and derived units and give
examples of derived units.
1.2.3 Convert between different units of quantities.
1.2.4 State units in the accepted SI format.
1.2.5 State values in scientific notation and in multiples of units with
appropriate prefixes.
1.2.6 Describe and give examples of random and systematic errors.
1.2.7 Distinguish between precision and accuracy.
1.2.8 Explain how the effects of random errors may be reduced.
1.2.9 Calculate quantities and results of calculations to the appropriate
number of significant figures.
1.2.10 State uncertainties as absolute, fractional and percentage uncertainties.
1.2.11 Determine the uncertainties in results.
1.2.12 Identify uncertainties as error bars in graphs.
1.2.13 State random uncertainty as an uncertainty range () and represent it
graphically as an error bar.
1.2.14 Determine the uncertainties in the slope and intercepts of a straightline graph.
1 The diameter of a proton is of the order of magnitude of
A 1012m. B 1015m. C 1018m D 1021m.
Exercise
If most of the atom is empty space
why does stuff feel so solid?
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
4/144
Physics and physical measurement
The SI system of fundamental and derived unitsIf you want to measure something, you have to use a unit. For example, it is useless
to say that a persons mass is 10, 60, 140 or 600 if we do not know whether it is
measured in kilograms or some other unit such as stones or pounds. In the old
days, units were rather random; your mass might be measured in stones, but your
height would not be measured in sticks, but in feet.
Soon after the French Revolution, the International System of units was developed.
They are called the SI units because SI stands for Systme International.
There are seven base, or fundamental, SI units and they are listed in the table
below.
Name Symbol Concept
metre or meter m length
kilogram kg mass
second s second
ampere A electric current
kelvin K temperature
mole mol amount of matter
candela cd intensity of light
Mechanics is the study of matter, motion, forces and energy. With combinations
of the first three base units (metre, kilogram and second), we can develop all the
other units of mechanics.
density mass
_______
volumekg m3
speed distance
_______
time m s1
As the concepts become more complex, we give them new units. The derived SI
units you will need to know are as follows:
Name Symbol ConceptBroken down intobase SI units
newton N force or weight kg m s2
joule J energy or work kg m2s2
watt W power kg m2s3
pascal Pa pressure kg m1s2
hertz Hz frequency s1
coulomb C electric charge As
volt V potential difference kg m2s3A1
ohm resistance kg m2s3A2
tesla T magnetic field strength kg s2A1
weber Wb magnetic flux kg m2
s2
A1
becquerel Bq radioactivity s1
Some people think the foot was
based on, or defined by, the length
of the foot of an English king, but it
can be traced back to the ancient
Egyptians.
The system of units we now call SI
was originally developed on the
orders of King Louis XVI of France.
The unit for length was defined
in terms of the distance from the
equator to the pole; this distance
was divided into 10 000 equal parts
and these were called kilometres.
The unit for mass was defined in
terms of pure water at a certain
temperature; one litre (or 1000 cm3)
has a mass of exactly one kilogram.
Put another way, 1 cm3of water
has a mass of exactly 1 gram.
The units of time go back to the
ancients, and the second was
simply accepted as a fraction
of a solar day. The base unit for
electricity, the ampere, is defined
in terms of the force between two
current-carrying wires and the unit
for temperature, the kelvin, comes
from an earlier scale developed by
a Swedish man called Celsius.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
5/145
Worked examples
1 Give units for the following expressed as (i)the derived unit (ii)base SI units:
(a) force
(b) kinetic energy.
2 Check if these equations work by substituting units into them.
(a) powerwork/time or energy/time
(b) powerforcevelocity
Solutions
1 (a) (i) N (ii) kg(m s2) or kg m s2
(b) (i) J (ii) kg (m s1)2or kg m2s2
2 (a) W : J/s or W : (kg m2s2)/s or W : kg m2s3
(b) W : N(m s1) or W : (kg m s2)(m s1) or W : kg m2s3
In addition to the above, there are also a few important units that are not
technically SI, including:
Name Symbol Concept
litre l volume
minute, hour, year, etc. min, h, y, etc. time
kilowatt-hour kWh energy
electronvolt eV energy
degrees celsius C temperature
decibel dB loudness
unified atomic mass unit u mass of nucleon
Examiners hint:
forcemass acceleration.
Examiners hint:
kinetic energy1
_
2
mv2
2 Which one of the following units is a unit of energy?
A eV B W s1 C W m1 D N m s1
3 Which one of the following lists a derived unit and a fundamental unit?
A ampere second
B coulomb kilogram
C coulomb newton
D metre kilogram
Exercises
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
6/146
Physics and physical measurement
Worked example
Convert these units to SI:.
(a) year (b)C (c) kWh (d)eV
Solution
(a) 1 year1 365 days 24 hours 60 minutes 60 seconds
3.15107s
(b) Here are some common conversions:
0 K273 C
273 K0 C
300 K27 C
373 K100 C
(c) 1 kWh (energy)1000 W (power) 3600 s (time)
3 600 000 J
3.6106J
(d) electrical energyelectric charge potential difference
1 eV 1.6 1019C 1 V
1.61019 J
The SI units can be modified by the use of prefixes such as millias in millimetre
(mm) and kiloas in kilometre (km). The number conversions on the prefixes are
always the same; millialways means one thousandth or 103and kiloalways means
one thousand or 10
3
.These are the most common SI prefixes:
Prefix Abbreviation Value
tera T 1012
giga G 109
mega M 106
kilo k 103
centi c 102
milli m 103
micro 106
nano n 109
pico p 1012
femto f 1015
Examiners hint: To change kilowatt-
hours to joules involves using the
equation:
energypower time.
1 kW1000 Wand 1 hour60 60 seconds.
Examiners hint: The electronvolt
is defined as the energy gained by an
electron accelerated through a potential
difference of one volt. So the electronvolt
is equal to the charge on an electron
multiplied by one volt.
4 Change 2 360 000 J to scientific notation and to M J.
5 A popular radio station has a frequency of 1 090 000 Hz. Change this to scientific notation and to MHz.
6 The average wavelength of white light is 5.0 107m. What would this be in nanometres?
7 The time taken for light to cross a room is about 1 108seconds. Change this intomicroseconds.
Exercises
Examiners hint: The size of one
degree Celsius is the same as one Kelvin
the difference is where they start, or the
zero point. The conversion involves adding
or subtracting 273. Since absolute zero or
0 K is equal to273 C, temperature in
Ctemperature in K 273.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
7/147
Uncertainty and error in measurementEven when we try to measure things very accurately, it is never possible to be
absolutely certain that the measurement is perfect.
The errors that occur in measurement can be divided into two types, randomand
systematic. If readings of a measurement are above and below the true value with
equal probability, then the errors are random. Usually random errors are causedby the person making the measurement; for example, the error due to a persons
reaction time is a random error.
Systematic errors are due to the system or apparatus being used. Systematic errors
can often be detected by repeating the measurement using a different method
or different apparatus and comparing the results. A zero offset, an instrument
not reading exactly zero at the beginning of the experiment, is an example of a
systematic error. You will learn more about errors as you do your practical work in
the laboratory.
Random errors can be reduced by repeating the measurement many times and
taking the average, but this process will not affect systematic errors. When you
write up your practical work you need to discuss the errors that have occurred in
the experiment. For example: What difference did friction and air resistance make?
How accurate were the measurements of length, mass and time? Were the errors
random or systematic?
Another distinction in measuring things is betweenprecisionand accuracy.
Imagine a game of darts where a person has three attempts to hit the bulls-eye.
If all three darts hit the double twenty, then it was a precise attempt, but not
accurate. If the three darts are evenly spaced just outside and around the bulls-eye,
then the throw was accurate, but not precise enough. If the darts all miss the board
entirely then the throw was neither precise nor accurate. Only if all three darts hitthe bulls-eye can the throws be described as both precise and accurate!
What conditions would be
necessary to enable something to
be measured with total accuracy?
Figure 1.2 All the players try to hit
the bulls eye with their three darts, but
only the last result is both precise and
accurate.
205
12
9
14
1
1
8
16
719 3 17
2
15
10
6
13
4
181 205
12
9
14
1
1
8
16
719 3 17
2
15
10
6
13
4
181
205
12
9
14
1
1
8
16
7
19 3 17
2
15
10
6
13
4
181 205
12
9
14
1
1
8
16
7
19 3 17
2
15
10
6
13
4
181
precise,
not accurate
neither precise
nor accurate
accurate,
not precise
both accurate
and precise
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
8/148
Physics and physical measurement
It is the same with measurements; they can be precise, accurate, neither or both. If
there have been a large number of measurements made of a particular quantity, we
can show these four possibilities on graphs like this:
Significant figures
When measuring something, in addition to a unit, it is important to think aboutthe number of significant figures or digits we are going to use.
For example, when measuring the width and length of a piece of A4 paper with a
30 cm ruler, what sort of results would be sensible?
Measurements (cm)Number of
significant figuresSensible?
21 30 1 2 yes
21.0 29.7 0.1 3 maybe
21.03 29.68 0.01 4 no
With a 30 cm ruler it is not possible to guarantee a measurement of 0.01 cm or
0.1 mm so these numbers are not significant.
This is what the above measurements of width would tell us:
Measurements (cm) Number ofsignificant figures
Value probablybetween (cm)
21 1 2 2022
21.0 0.1 3 20.921.1
21.03 0.01 4 21.0221.04
The number of significant figures in any answer or result should not be more than
that of the least precise value that has been used in the calculation.
precise but
not accurate
true value ofmeasured quantity
number ofreadings
number ofreadings
number ofreadings
number ofreadings
accurate but
not precise
true value
neither accurate
nor precise
true value
accurate and precise
true value
Figure 1.3 Here is another way of
looking at the difference between
precision and accuracy, showing the
distribution of a large number of
measurements of the same quantity
around the correct value of the
quantity.
If you are describing a person
you have just met to your best
friend, which is more important
accuracy, precision or some other
quality?
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
9/149
Worked example
Calculate the area of a piece of A4 paper, dimensions 21 cm 29.7 cm. Give your
answer to the appropriate number of significant figures.
Solution
21 29.7623.7
Area620 cm2
6.2102cm2
Uncertainties in calculated results
If we use a stopwatch to measure the time taken for a ball to fall a short distance,
there will inevitably be errors or uncertainties due to reaction time. For example, if
the measured time is 1.0 s, then the uncertainty could reasonably be0.1 s. Here
the uncertainty, or plus or minus value, is called an absolute uncertainty. Absolute
uncertainties have a magnitude, or size, and a unit as appropriate.
There are two other ways we could show this uncertainty, either as a fraction or asa percentage. As a fraction, an uncertainty of 0.1 s in 1.0 s would be 1__10and as a
percentage it would be 10%.
These uncertainties increase if the measurements are combined in calculations or
through equations. In an experiment to find the acceleration due to gravity, the
errors measuring both time and distance would influence the final result.
If the measurements are to be combined by addition or subtraction, then the
easiest way is to add absolute uncertainties. If the measurements are to be
combined using multiplication, division or by using powers like x2, then the best
method is to add percentage uncertainties. If there is a square root relationship,
then the percentage uncertainty is halved.
Uncertainties in graphs
When you hand in your lab reports, you must always show uncertainty values
at the top of your data tables asa sensible value. On your graphs, these are
represented as error bars. The error bars must be drawn so that their length on
the scale of the graph is the same as the uncertainty in the data table. Error bars
can be on either or both axes, depending on how accurate the measurements are.
The best-fit line must pass through all the error bars. If it does not pass through
a point, then that point is called an outlier and this should be discussed in the
evaluation of the experiment.
Examiners hint: The least precise
input value, 21 cm, only has 2 significant
figures.
Examiners hint: Because we are
using scientific notation, there is no
doubt that we are giving the area to 2
significant figures.
8 When a voltage Vof 12.2 V is applied to a DC motor, the current Iin the motor is 0.20 A. Which
one of the following is the output power VIof the motor given to the correct appropriate
number of significant digits?
A. 2 W B. 2.4 W C. 2.40 W D. 2.44 W
Exercise
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
10/1410
Physics and physical measurement
Scalarsare measurements that have size, or magnitude. A scalar almost always
needs a unit. Vectorshave magnitude and also have a direction. For example, a
Boeing 747 can fly at a speed of 885 kmh1or 246 ms1. This is the speed and is a
scalar quantity. If the plane flies from London to New York at 246 ms1then this
is called its velocity and is a vector, because it tells us the direction. Clearly, flying
from London to New York is not the same as flying from New York to London;
the speed can be the same but the velocity is different. Direction can be crucially
important.
1.0O
2.0
time (s)0.2
outlier
distance
(m)0.1
3.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
y
x
Motion showing a body travelling at a steady speedFigure 1.4 Error bars can
be on thex-axis only,
y-axis only or on both
axes, as shown here.
Vectors and scalars1.3
Assessment statements
1.3.1 Distinguish between vector and scalar quantities, and give examples ofeach.
1.3.2 Determine the sum or difference of two vectors by a graphical method.
1.3.3 Resolve vectors into perpendicular components along chosen axes.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
11/1411
Here is another example of the difference between a vector and a scalar. Suppose
you walk three metres to the east and then four metres towards the north.
The distance you have travelled is seven metres but your displacement, the distance
between where you started and where you ended up, is only five metres. Because
displacement is a vector, we also need to say that the five metres had been moved
in a certain direction north of east.
Here are some common examples:
Scalar Vector
Distance Displacement
Speed Velocity
Temperature Acceleration
Mass Weight
All types of energy All forces
Work Momentum
Pressure All field strengths
A vector is usually represented by a bold italicized symbol, for example F for force.
Free body diagrams
4
m north
distance walked7
m
displacement5m (north of east)
3
m east
5
m
Figure 1.5 Distance is a scalar, and
in this case, the distance travelled is
3 m4 m7 m. Displacement is a
vector, and here it is the hypotenuse of
the triangle (5 m).
9 Which oneof the following is a scalar quantity?
A Pressure B Impulse
C Magnetic field strength D Weight
10 Which oneof the following is a vector quantity?
A Electric power B Electrical resistance
C Electric field D Electric potential difference
Exercises
weightliftthrustdrag
lift
thrust of jets
weight
drag of air
weightnormal force
weight
normal orsupporting force
Figure 1.6 Free-body diagrams show
all the forces acting on the body. The
arrows should be drawn to represent
both the size and direction of the forces
and should always be labelled.(c) Aeroplane in level flight acceleratingto the right:
(a) Book resting on a table: (b) Car travelling at constant velocityto the left:
weightnormal forcesdriving forceresistive forces
weight
normal forces
resistive forcesdriving force
of engine
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
12/1412
Physics and physical measurement
If two or more forces are acting at the same point in space, you need to be able to
calculate the resultant, or total effective force, of the combination. The resultant is
the single force that has the same effect as the combination.
If they are not parallel, the easiest way to determine the resultant is by the
parallelogram law. This says that the resultant of two vectors acting at a point is
given by the diagonal of the parallelogram they form.
You also need to be able to resolve, or split, vectors into components or parts. A
component of a vector shows the effect in a particular direction. Usually we resolve
vectors into an x-component and ay-component.
Worked example
A force of 20 N pulls a box on a bench at an angle of 60 to the horizontal. What is
the magnitude of the force Fparallel to the bench?
Figure 1.7 When the vectors are
parallel, the resultant is found by simple
addition or subtraction.
(a) (b)
(c)
2
N 3
N
resultant5N to right
2
N 3
N
resultant1N to left
3N
3N
6N
resultantzero
10
N
6
N resultant
magnitude of resultant14
N
60
Figure 1.8 We can use a graphical
method to find the resultant accurately.
Examiners hint: You can do this is
by scale drawing using graph paper.
11 The diagram below shows a boat that is about to cross a river in a direction perpendicular to the
bank at a speed of 0.8 ms1. The current flows at 0.6 ms1in the direction shown.
The magnitude of the displacement of the boat 5 seconds after leaving the bank is
A 3 m. B 4 m. C 5 m. D 7 m.
Exercise
bank
bank
0.6
ms1
0.8
ms1
boat
y-component
x-component (F)A
B20
N
C60
Figure 1.9 Resolving into
components is the opposite process
to adding vectors and finding the
resultant.
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
13/1413
Solution
The string will tend to pull the box along the bench but it will also tend to pull it
upwards.
cosine 60adjacent
__________
hypotenuse
F___
20
F20 N cos 6010 N
Examiners hint: In the right-angled
triangle ABC, thex-component (F) is
adjacent to the 60 angle while the 20 N
force is the hypotenuse.
12 A force of 35 N pulls a brick on a level surface at an angle of 40 to the horizontal. The frictional
force opposing the motion is 6.8N. What is the resultant force Fparallel to the bench?
Exercise Examiners hint: Here is an example
of how notto answer a basic question:
Findx.
x
3cm
4cmHereitis
1 Which one of the following contains three fundamental units?
A Metre Kilogram Coulomb
B Second Ampere Newton
C Kilogram Ampere Kelvin
D Kelvin Coulomb Second
2 The resistive force Facting on a sphere of radius rmoving at speed vthrough a liquid is
given by
Fcvr
where cis a constant. Which of the following is a correct unit for c?
A N
B N s1
C N m2s1
D N m2s
3 Which of the following is nota unit of energy?
A W s
B W s1
C k Wh
D k g m2s2
4 The power Pdissipated in a resistor Rin which there is a current Iis given by
PI 2R
The uncertainty in the value of the resistance is10% and the uncertainty in the value
of the current is 3%. The best estimate for the uncertainty of the power dissipated is
A 6%
B 9%
C 6%
D 19%
actice questions
downloaded from www.pearsonbaccalaureate.com/diploma
UNCORRECTED PROOF COPY
7/24/2019 Pearson Baccalaureate Physics SL Chapter1
14/14
Physics and physical measurement
Here are some ideas to help you with the estimates on page 3:
1 How high is a two floor house in metres?
First we could think about how high a normal room is. When you stand up
how far is your head from the ceiling? Most adults are between 1.5 m and 2.0 m
tall, so the height of a room must be above 2.0 m and probably below 2.5 m.
If we multiply by two and add in some more for the floors and the roof then asensible value could be 7 or 8 m.
2 What is the diameter of the pupil of your eye?
This would change with the brightness of the light, but even if it were really
dark it is unlikely to be above half a centimetre or 5.0 mm. In bright sunshine
maybe it could go down to 1.0 mm so a good estimate would be between these
two diameters.
3 How many times does your heart beat in an hour when you are relaxed?
You can easily measure your pulse in a minute. When you are relaxed it willmost probably be between 60 and 80 beats per minute. To get a value for an
hour we must multiply by 60, and this gives a number between 3600 and 4800.
As an order of magnitude or ball park figure this would be 103.
4 What is the weight of an apple in newtons?
Apples come in different sizes but if you buy a kilogram how many do you get?
If the number is somewhere between 5 and 15 that would give an average mass
for each apple of around 100g which translates to a weight of approximately 1
N.
5 What is the mass of the air in your bedroom?
To estimate this you need to know the approximate density of air, which is
1.3 kg m3. Then you need an estimate of the volume of your bedroom, for
example 4 m 3 m 2.5 m, which would give 30 m3.
Then massdensity volume would give around 40 kg; maybe more than
expected.
6 What pressure do you exert on the ground standing on one foot?
For this we would use the equation pressureforce
_____
area. The force would be
your weight; if your mass is 60 kg then your weight would be 600 N. If we take
average values for the length and width of your foot as 30 cm and 10 cm, change
them to 0.3 m and 0.1 m, and multiply, then the area is 0.03 m2. Dividing 600 N
by 0.03 m2gives an answer of 20 000 Pa.
You need to practise these kinds of estimations without a calculator.
If air is that heavy then why dont
we feel it?
How does the pressure exerted
by one foot compare to blood
pressure and atmospheric
pressure?
What would happen to an
astronaut in space if their space suit
suddenly ripped open?
downloaded from www.pearsonbaccalaureate.com/diploma
Top Related