IB Physics Terms 1

1.2.1.2 Giving examples if needed. clarify the concept of a derived quantity.

A derived quantity can be a defined quantity, but it will be dependent on two or more fundamental quantities, or a combination of one unit (for example area = distance^2)

1.2.1.1 Define a fundamental quantity.

A fundamental quantity is one which is defined and has no dependence on any other quantity.

1.2.10.1.c) Define absolute error.

Absolute error is the error associated wth a measurement.

1.2.1.6 Derived Quantities

Acceleration, Charge. Electric Field Strength, Electrical Potential, Electrical Resistance, Energy, Force, Frequency, Heat Capacity, Magnetic Field Strength, Magnetic Flux, Momentum, Power, Pressure, Radioactivity, Specific Heat Capacity, Velocity

1.2.1.3 Using density as your example, explain the difference between a fundamental unit and a derived unit.

Density is defined as the mass per unit volume of a substance and is measured in kgm^-3 which is a combination of the fundamental units for mass (kg) and distance (m). Note that the quantity volume is also a derived quantity, depending on distance cubed.

1.2.10.1.d) Define fractional or relative uncertainty.

Fractional uncertainty is equal to the ratio of the absolute uncertainty to the measurement.

1.2.6.4 Explain four ways of reducing systematic errors.

It is important to realize that systematic errors cannot be reduced by taking multiple readings because they are often caused by errrors in the instruments and/or the operators themselves. Systematic errors can be reduced by using the most accurate equipment available, by having different operators check the readings, by ensuring that readings are taken carefully and correctly by ensuring there is no zero error in an instrument.

Momentum

Kilogram metres per second=kg m s^-1 Dependent on (kg)(m)(s^-1)

1.2.1.5 the Seven Fundamental Quantities

Mass, Length, Time, Electric Current, Amount of a Substance, Temperature, Luminosity

1.1.1.3 Discuss when it is appropriate to use orders of magnitude in answers and when it is appropriate to give exact answers.

Orders of Magnitude -when numbers are really large or really small -when you are asked for an 'indication' of size rather than exact measurement Exact Answer -when precise measurements are required -when numbers are in 'normal' ranges

1.2.10.1.f) Define percentage discrepancy.

Percentage discrepancy is equal to the difference between an experimental result and an accepted value value expressed as a percentage of the accepted value.

1.2.10.1. e) Define percentage uncertainy.

Percentage uncertainty is fractional uncertainty expressed as a percentage (i.e. fractional uncertainty * 100)

1.2.6.1 Describe, and give five examples of a random error.

Random errors are caused by uncertainties in measuring instruments, mistakes by people and uncontrolled external factors. They include things like ambient temperature variations, misreading scales, parallaz error, vibrations affecting equipment, air currents, incorrect calculations, use of incorrect formulas, variations in the characteristics of the data being collected.

1.2.6.2 Explain four ways of reducing random errors.

Random errors can be reduced by taking multiple readings and using average values. This will produce a measurement which will be closer to the true value than many of the individual readings. Random error can also be reduced by using more accurate measuring instruments and by having consistent experimental procedures. Both of these strategies will reduce the magnitude of any variations in readings. Random error is also reduced by controlling or eliminating all other factors which might influence the measurement. This will also reduce the variation in repeated measurements.

1.2.1.4 What is an SI unit and why are they used?

SI refers to the Standard International Units, a system of units for quantitiies used (almost) worldwide so that communication between scientists is faster, easier and better understood.

1.3.1.1 Distinguish between a scalar and a vector quantity.

Scalar quantities only require magnitude, vector quantities need magnitude and direction to fully define them.

1.2.6.3 Descibe, and give five examples of a systematic error.

Systematic errors cause experimental results to be spread around a value which is not necessarity the accepted value. They include incorrectly calibrated instruments, poor reaction time of the experimenter, consistent parallax error, poor quality instruments, and instrument zero errors.

1.2.7.1 Define the accuracy of a measurement. How is the accuracy of a measurement indicated?

The accuracy of a measurement is an indication of how close that measurement is to the accepted value of the measure. Accuracy is indicated by the inclusion of relative or percentage errors when reporting the measurement.

1.2.10.1.a) Define limit of reading of a measuring instrument.

The limit of reading of an instrument is defined as equal to the smallest scale division on the scale of the instrument.

1.2.10.1.b) Define maximum degree of uncertainty of a measuring instrument.

The maximum degree of uncertainty of an instrument is half the limit of reading of that instrument.

1.2.7.2 Define the precision of a measurement. How is the precision of a measurement indicated?

The precision of a measurement is an indication of the agreement between repeated measurements made in the same way. Precision is indicated by the absolute error in a measurement.

Electric Current

ampere=A

Radioactivity

becquerel=Bq Dependent on -

Heat Capacity

calorie=C Dependent on (J)(K^-1)

Specific Heat Capacity

calorie=c Dependent on (m^2)(s^-2)(K^-1)

Luminosity

candela=Cd

Charge

coulomb=C Dependent on (A)(s)

Frequency

hertz=Hz Dependent on s^-1

Energy

joule=J Dependent on (kg)(m^2)(s^-2)

Temperature

kelvin=K

Mass

kilogram=kg

Length

meter=m

Velocity

metres per second Dependent on (m)(s^-1)

Acceleration

metres per second per second=ms^-2 Dependent on (m)(s^-2)

Amount of a Substance

mole=mol

Force

newton=N Dependent on (kg)(m)(s^-2)

Electrical Resistance

ohm= Dependent on (kg)(m^-2)(s^-3)(A^-2)

Pressure

pascal=Ps Dependent on (kg)(m^-1)(s^-1)

Time

seconds=s

Magnetic Field Strength

tesla=T Dependent on (kg)(s^-2)(A^-1)

1.1.1.1 Define what is meant by 'order of magnitude.'

the power of ten closest to the number

Electrical Potential

volt=V Dependent on (kg)( m^2)(s^-3)(A^-1)

Electric Field Strength

volts per metre=E Dependent on (V)(m^-1)

Power

watt=W Dependent on (kg)(m^2)(s^-3)

Magnetic Flux

weber= Dependent on (kg)(m^2)(s^-2)(A^-1)