Topic 1 - Working As A Physicist (All Papers) Flashcards
List the seven base quantities
Mass
Length
Time
Current
Temperature
Amount of Substance
Luminous intensity
List the seven base units
Kilogram (kg)
Metre (m)
Second (s)
Ampere (A)
Kelvin (K)
Mole (mol)
Candela (cd)
What are the SI units of Force?
- Force = Mass x Acceleration
- Force = kg x ms^-2
- Force = kgms^-2
List every prefix along with their symbol and multiplier
- Peta P x10^15
- Tera T x10^12
- Giga G x10^9
- Mega M x10^6
- Kilo k x10^3
- Centi c x10^-2
- Milli m x10^-3
- Micro u x10^-6
- Nano n x10^-9
- Pico p x10^-12
- Femto f x10^-15
Convert 60nm to m
- 60 x 10^-9
- = 6 x 10^-8 m
- = 0.00000006m
Convert 87MJ to J
- 87 x 10^6 J
- = 87,000,000 J
Convert 6pF to F
- 6 x 10^-12 F
Convert 9 gigaohms to ohms
- 9 x 10^9 Ohms
Convert 10um to m
- 10 x 10^-6 m
- = 1 x 10^-5 m
Define resolution:
- The smallest measuring interval and the source of uncertainty in a single reading.
Define uncertainty:
- The the interval within which the true value can be considered to lie with a given level of confidence or probability.
Define systematic error.
- A systematic error is a fault with the equipment.
- These errors are usually in one direction (e.g results all too low/high) and can be compensated for.
Define human error.
- A random error is usually due to human error in taking the readings.
- These are always given as plus or minus uncertainties.
- They affect precision.
Define error.
- The difference between the measurement result and the true value if a true value
is thought to exist. - This is not a mistake in the measurement. The error can be due to both systematic and random effects and an error of unknown size is a source of uncertainty.
How to estimate absolute uncertainty:
- Half the resolution of the instrument
OR if the readings are repeated: - half the range of the repeats and a mean calculated for the main reading.
How to calculate percentage uncertainty:
(Absolute Uncertainty / Actual Reading) x 100
Define accurate.
- A measurement result is considered accurate if it is judged to be close to the true value.
Define precise.
- A quality describing the closeness of agreement (consistency) between values obtained by repeated measurement.
Compounding Uncertainties 1:
When the measured quantities are multiplied or divided, _____________________
- The percentage uncertainties are added!
Compounding Uncertainties 2:
If the quantities are squared or cubed in the calculation, ___________________
- You multiply the uncertainty by the power!
Steps on how to use vernier scales:
- STEP 1: Where does the first line on the bottom scale roughly line up with on the top one?
- STEP 2: Where does a second line on the bottom scale EXACTLY line up with one on the top one?
- STEP 3: The first reading represents 0.x mm and the second reading represents 0.0x mm. Add these together.
Steps on how to use Micrometers:
- STEP 1: Where does the EDGE of the vertical scale approximately line up with the horizontal?
- STEP 2: Has it passed the half way mark?
- STEP 3: Then add the reading from the side scale onto it.
Compounding Uncertainties 3:
If adding or subtracting data, _____________
- Add absolute uncertainties
To reduce random errors (3 ways):
- Take at least 3 repeats and calculate a mean, allowing anomalies to be identified.
- Use computers/data loggers/cameras to reduce human error and enable smaller intervals.
- Use appropriate equipment e.g a micrometer has a higher resolution than a ruler.
