Measurements in Physics (DP IB Physics)

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  • What is a derived unit?

    A derived unit is one that is made up of combinations of SI units.

  • What is the SI base unit for mass?

    The SI base unit for mass is kilograms (kg).

  • True or False?

    The SI base unit for the newton is kg m s–1.

    False.

    The SI base unit for the newton is kg m s–2

  • What is the SI base unit for length?

    The SI base unit for length is metres (m).

  • True or False?

    The SI base unit for the joule is kg m s–2.

    False.

    The SI base unit for the joule is kg m2 s–2.

  • What is the SI base unit for time?

    The SI base unit for time is seconds (s).

  • True or False?

    The SI base unit for the watt is kg m2 s–3.

    True.

    The SI base unit for the watt is kg m2 s–3.

  • What is the SI base unit for current?

    The SI base unit for current is amperes, or amps (A).

  • True or False?

    The SI base unit for the pascal is kg m–1 s–2.

    True.

    The SI base unit for the pascal is kg m–1 s–2

  • What is the SI base unit for temperature?

    The SI base unit for temperature is the kelvin (K).

  • True or False?

    The SI base unit for frequency is hertz (Hz).

    False.

    The unit for frequency is hertz (Hz), but the SI base unit is s–1.

  • What is the SI base unit for the amount of a substance?

    The SI base unit for the amount of a substance is the mole (mol).

  • What is the order of magnitude of 6.32 cross times 10 to the power of 8?

    The order of magnitude of 6.32 cross times 10 to the power of 8 is: 10 to the power of 9

  • What is the order of magnitude of 1.60 cross times 10 to the power of negative 19 end exponent?

    The order of magnitude of 1.60 cross times 10 to the power of negative 19 end exponent is: 10 to the power of negative 19 end exponent

  • What is the order of magnitude of 7.81 cross times 10 to the power of negative 9 end exponent?

    The order of magnitude of 7.81 cross times 10 to the power of negative 9 end exponent is: 10 to the power of negative 8 end exponent

  • True or False?

    1000 is one order of magnitude larger than 100.

    True.

    One order of magnitude larger is ten times larger.

    • 10 space cross times space 100 space equals space 1000

  • True or False?

    10 to the power of 28 is two orders of magnitude larger than 5.6 cross times 10 to the power of 26.

    False.

    Two orders of magnitude larger than 5.6 cross times 10 to the power of 26 is 10 to the power of 29.

    The order of magnitude of 5.6 cross times 10 to the power of 26 is 10 to the power of 27.

    Two orders of magnitude larger is one hundred times larger.

    • 10 to the power of 27 space cross times space 10 squared space equals space 10 to the power of 29

  • Estimate the order of magnitude of the diameter of a hydrogen atom.

    The order of magnitude of the diameter of a hydrogen atom is tilde 10 to the power of negative 10 end exponentm.

  • Estimate the order of magnitude of the length of a car.

    The order of magnitude of the length of a car is tilde 10 to the power of 0 m.

  • Estimate the order of magnitude of the diameter of the Earth.

    The order of magnitude of the diameter of the Earth is tilde 10 to the power of 7 m.

  • What is 426 space 019 in scientific notation to one significant figure?

    426 space 019 in scientific notation to one significant figure is 4 cross times 10 to the power of 5.

  • What is 105 space 026 space 132 in scientific notation to two significant figures?

    105 space 026 space 132 in scientific notation to two significant figures is 1.1 cross times 10 to the power of 8.

  • What is 0.002053 in scientific notation to two significant figures?

    0.002053 in scientific notation to two significant figures is 2.1 cross times 10 to the power of negative 3 end exponent.

  • True or False?

    All digits of an integer number are significant if the last digit is non-zero.

    True.

    All digits of an integer number are significant if the last digit is non-zero.

    • For example, 702 has 3 significant figures

  • True or False?

    Zeros at the end of an integer number are always significant.

    False.

    Zeros at the end of an integer number are never significant.

    • For example, 306 000 has 3 significant figures

  • True or False?

    Zeros in front of an integer number are never significant.

    True.

    Zeros in front of an integer number are never significant.

    • For example, 0.025 has 2 significant figures

  • True or False?

    Zeros at the end of a number less than one are never significant.

    False.

    Zeros at the end of a number less than one are always significant.

    • For example, 0.02000 has 4 significant figures

  • True or False?

    Zeros after an integer number that has a decimal point are always significant.

    True.

    Zeros after an integer number that has a decimal point are always significant.

    • For example, 40.0 has 3 significant figures

  • What is dimensional analysis?

    Dimensional analysis is a method used to check the homogeneity of physical equations by studying the units.

  • Show that the equation space p space equals space m v is a homogeneous equation.

    An equation is homogeneous if the SI base units are the same on both sides.

    • p space equals space m v

    • open square brackets kg space straight m space straight s to the power of negative 1 end exponent close square brackets space equals space open square brackets kg close square brackets space cross times space open square brackets straight m space straight s to the power of negative 1 end exponent close square brackets

    • open square brackets kg space straight m space straight s to the power of negative 1 end exponent close square brackets space equals space open square brackets kg space straight m space straight s to the power of negative 1 end exponent close square brackets

  • Show that the equation E subscript k space equals space fraction numerator p squared over denominator 2 m end fraction is a homogeneous equation.

    An equation is homogeneous if the SI base units are the same on both sides.

    • E subscript k space equals space fraction numerator p squared over denominator 2 m end fraction

    • open square brackets kg space straight m squared space straight s to the power of negative 2 end exponent close square brackets space equals space fraction numerator open square brackets kg squared space straight m squared space straight s to the power of negative 2 end exponent close square brackets over denominator open square brackets kg close square brackets end fraction

    • open square brackets kg space straight m squared space straight s to the power of negative 2 end exponent close square brackets space equals space open square brackets kg space straight m squared space straight s to the power of negative 2 end exponent close square brackets

  • Show that the equation P space equals space F v is a homogeneous equation.

    An equation is homogeneous if the SI base units are the same on both sides.

    • P space equals space F v

    • fraction numerator open square brackets kg space straight m squared space straight s to the power of negative 2 end exponent close square brackets over denominator open square brackets straight s close square brackets end fraction space equals space open square brackets kg space straight m space straight s to the power of negative 2 end exponent close square brackets space cross times space open square brackets straight m space straight s to the power of negative 1 end exponent close square brackets

    • open square brackets kg space straight m squared space straight s to the power of negative 3 end exponent close square brackets space equals space open square brackets kg space straight m squared space straight s to the power of negative 3 end exponent close square brackets

  • Show that the equation T space equals space 2 straight pi square root of m over k end root is a homogeneous equation.

    An equation is homogeneous if the SI base units are the same on both sides.

    • T space equals space 2 straight pi square root of m over k end root

    • fraction numerator 1 over denominator open square brackets straight s close square brackets end fraction space equals space square root of fraction numerator open square brackets kg close square brackets over denominator open square brackets straight N space straight m to the power of negative 1 end exponent close square brackets end fraction end root equals space space square root of fraction numerator open square brackets kg close square brackets over denominator open square brackets kg space straight m space straight s to the power of negative 2 end exponent close square brackets open square brackets straight m to the power of negative 1 end exponent close square brackets end fraction end root

    • fraction numerator 1 over denominator open square brackets straight s close square brackets end fraction space equals space square root of fraction numerator 1 over denominator open square brackets space straight s to the power of negative 2 end exponent close square brackets end fraction end root space equals space fraction numerator 1 over denominator open square brackets straight s close square brackets end fraction

  • Define the term resolution of a measuring instrument.

    The resolution of a measuring instrument is the smallest change in the physical quantity being measured that results in a change in the reading given by the measuring instrument.

  • What steps need to be taken for an experiment to be valid.

    For an experiment to be valid, any variable that may affect the results needs to be controlled for.

  • Why is it important to calibrate measuring equipment prior to taking any readings?

    It is important to calibrate measuring equipment prior to taking any readings to make sure the values given by the measuring device are accurate.

  • What is an independent variable?

    An independent variable is a variable that is changed on purpose in order to observe the effects of the change.

  • What is a dependent variable?

    A dependent variable is a variable that changes in response to changing the independent variable. The effects of this change are predicted, observed, and measured.

  • What is a control variable?

    A control variable is any other factor that may affect the results of the investigation and must therefore be controlled for as far as possible.

  • A student is measuring the terminal velocity of a ball bearing in different fluids.

    State the following variables for this investigation:

    • independent variable

    • dependent variable

    • control variables

    For a student measuring the terminal velocity of a ball bearing in different fluids, the variables are as follows:

    • independent variable - terminal velocity of ball bearing

    • dependent variable - type of fluid

    • control variables - height of free fall, diameter and mass of ball bearing