Foundations of Physics Flashcards

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1
Q

What are physical quantities?

A

They consist of a numerical magnitude and a unit - to represent a physical quantity, it must contain both a numerical value and the units its measured in

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2
Q

What is the estimation for the diameter of an atom?

A

10^-10 m

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3
Q

What is the estimation for the wavelength of UV light?

A

10 nm

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4
Q

What is the estimation for the distance between the earth and the sun (1AU)?

A

1.5 x 10^8 m

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5
Q

What is the estimation for mass of a hydrogen atom?

A

10^-27 kg

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6
Q

What is the estimation for the mass of an adult human?

A

70kg

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7
Q

What is the estimation for the mass of a car?

A

1000 kg

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8
Q

What is the estimation for seconds in a year?

A

3 x 10^7 s

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9
Q

What is the estimation for the power of a lightbulb?

A

60 W

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10
Q

What is the estimation for atmospheric pressure?

A

1 x 10^5 Pa

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11
Q

What are the 7 SI base units?

A
  • Kilogram, kg (mass)
  • Metre, m (length)
  • Second, s (time)
  • Ampere, A (current)
  • Kelvin, K (temperature)
  • Mole, mol (temperature)
  • Candela, cd (luminosity
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12
Q

What are derived units?

A

Units of a quantity that are based solely on the 7 SI base units

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13
Q

What is the derived SI base unit of the newton?

A

kg ms^-2

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14
Q

What is the derived SI base unit of the joule?

A

kg m^2 s^-2

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15
Q

What is the derived SI base unit of the pascal?

A

kg m^-1 s^-2

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16
Q

What is homogeneity?

A

When something is all the same or of the same kind

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17
Q

How do you check the homogeneity of a physical equation?

A
  • Check the units on both sides of an equation
  • Determine if they are equal
  • If they do not match, the equation will need to be adjusted
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18
Q

What is the order of prefixes?

A

POSITIVE
kilo, mega, giga, tera, peta
NEGATIVE
milli, micro, nano, pico, femto

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19
Q

What is the centi prefix?

A

10^-2

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20
Q

What is the micro prefix?

A

10 ^-6

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21
Q

What is the general convention for tables?

A
  • Independent variable in the left column
  • Dependant variable in the right column
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22
Q

What is the general convention for graphs?

A
  • Independent variable plotted on the x-axis
  • Dependant variable plotted on the y-axis
23
Q

What is uncertainty?

A

An estimate of the difference between a measurement reading and the true value

24
Q

What leads to uncertainty?

A

Errors

25
Q

What are the 2 main types of error?

A

Random and systematic

26
Q

What is random error?

A

Error that causes unpredictable fluctuations in an instruments reading as a result of uncontrollable factors, such as environment

27
Q

How can you reduce random error?

A

Take repeat measurements several times and calculate an average from them

28
Q

What is systematic error?

A

Error that arises from the use of faulty instruments or from flaws in the experimental method. This type of error is repeated consistently every time the instrument is used or the method is followed, which affects the accuracy of all readings obtained

29
Q

How can you reduce systematic error?

A
  • Instruments should be recalibrated or different instruments should be used
  • Corrections and adjustments should be made to the technique
30
Q

What is a zero error?

A

A type of systematic error which occurs when an instrument gives a reading when the true reading is 0

31
Q

What are precise measurements?

A

Ones in which there is very little spread about the mean value

32
Q

What are accurate measurements?

A

Measurements close to the true value

33
Q

What is absolute uncertainty?

A

Where uncertainty is given as a fixed quantity

34
Q

What is percentage uncertainty?

A

Where uncertainty is given as a percentage of the measurement

35
Q

What is the calculation for percentage uncertainty?

A

Percentage uncertainty = (uncertainty/ measured value) x 100

36
Q

How do you calculate uncertainty in a reading?

A

+ or - half the smallest division

37
Q

How do you calculate uncertainty in repeated data?

A

Half the range

38
Q

How do you calculate the combined uncertainty when adding/ subtracting data?

A

Add the absolute uncertainties

39
Q

How do you calculate the combined uncertainty when multiplying/ dividing data?

A

Add the percentage uncertainties

40
Q

How do you calculate the combined uncertainty when raising data to a power?

A

Multiply the percentage uncertainty by the power - multiply this by the value you are finding the uncertainty of to get the absolute uncertainty

41
Q

What are error bars?

A

Plotted on graphs to show the absolute uncertainty of values plotted

42
Q

How do you calculate the uncertainty in a gradient?

A

Draw 2 lines of best fit:
- Line of best fit = passes as close to the points as possible
- Line of worst fit = the steepest or shallowest possible line which fits within all error bars

Percentage gradient = (best gradient - worst gradient) / best gradient x 100

43
Q

What is the percentage difference equation?

A

Percentage difference = (measured value - accepted value) / accepted value x 100

44
Q

The smaller the percentage difference, the _____ accurate the results of the experiment

A

More

45
Q

What is a scalar quantity?

A

A quantity which only has magnitude

46
Q

What is a vector quantity?

A

A quantity which has both magnitude and direction

47
Q

What are examples of scalar quantities?

A
  • Distance
  • Speed
  • Mass
  • Time
  • Energy
  • Volume
  • Density
  • Pressure
  • Electric charge
  • Temperature
48
Q

What are examples of vector quantities?

A
  • Displacement
  • Velocity
  • Acceleration
  • Force
  • Momentum
49
Q

How can you combine perpendicular vectors that are directed in the same direction?

A

Add them together

50
Q

How can you combine perpendicular vectors that are directed in opposite directions?

A

Take them away from one another - the vector you take away from is the resultants direction

51
Q

What is the sine rule?

A

A/ sin a = B/ sin b

52
Q

What is the cosine rule?

A

a^2 = b^2 + c^2 - 2bc cos θ

53
Q

What is the horizontal component of a force?

A

F cosθ

54
Q

What is the vertical component of a force?

A

F sinθ