Topic 1: Working as a Physicist

What are the seven base quantities?

. Mass - Kilogram (kg)

. Length - meter (m)

. Time - seconds (s)

. Amount of substance - mole (mol)

. Temp - degrees (°C)

. Electric current - Amps (A)

. Luminosity - Candela (Cd)

What are derived quantities?

. Any quantity derived from the 7 base quantities

.ie: force, velocity

What are the prefixes?

. Peta - 1 × 10^15

. Tera - 1 × 10^12

. Giga - 1 × 10^9

. Mega - 1 × 10^6

. Kilo - 1 × 10^3

. Milli - 1 × 10^-3

. Micro - 1 × 10^-6

. Nano - 1 × 10^-9

. Pico - 1 × 10^-12

. Femto - 1 × 10^-15

What is accuracy?

. Refers to how close a measurement is true to the accepted value

What is precision?

. Refers to how close measurements of the same item are to each other

What is a random error?

. Cause differences in measurements which causes a spread about the mean

. Affects precision

. ie: parallax error

What is a systematic error?

. Consistent, repeatable error

. Affects accuracy

. Associated with faulty equipment or a flawed experiment design

. ie: forgetting to tare a balance

How do you reduce random error?

. Take 3 readings, remove anomalies, calculate a mean

. Use computers/ data loggers to reduce human error and allow smaller time intervals

. Use appropriate equipment, ie: a micrometer

How do you reduce systematic error?

. Calibrate apparatus using a known value

. In radiation experiments, correct for background radiation by measuring it beforehand

How does estimating values for a physical quantity solve problems?

. Estimates can be used to predict range in which the results will lie in, so if an enormous anomaly occurs it can be identified as anomalous.

What is uncertainty?

. The bounds in which the accurate value can be expected to lie

. Can be given as a fixed quantity, or the percentage of a measurement

How do you reduce percentage uncertainty?

. Measure larger quantities

What is a reading?

. When one value is found

. ie: reading a thermometer

. The uncertainty is +/- half the smallest division

What is a measurement?

. When the difference between two readings is found

. ie: reading a ruler, as both the starting point and end point are judged

. The uncertainty is at least +/- 1 smallest division, or the uncertainty of each side added up

what is the uncertainty of digital readings?

. Values will either have the uncertainty quoted, or assumed to be +/- the last significant digit

What is the uncertainty for repeated data?

. Uncertainty is half the range

. mean +/- half the range

How do you combine percentage uncertainties?

. When adding/subtracting data, absolute uncertainties are added

. When multiplying/dividing data, percentage uncertainties are added

. When raising to a power, multiply percentage uncertainty by the power

How does society use science to inform decision making?

. Government policy making

. Criminal justice- ie: analysis of evidence

. Everyday life- ie: lifestyle

What is an implication of science?

. A direct/implied consequence of the knowledge of a particular concept

. Can be commercial, legal, ethical, social

. ie: there are legal implications of human genome mapping-copyright, as well as ethical implications

What is an application of science, and what are the risks?

. A use of scientific knowledge in order to carry out a specific action, ie: developing a medical treatment

. A radiation treatment designed as a treatment for cancer has benefits (saving lives) and risks (accidents in new technology could cause injury or death)

What is the role of the scientific community in validating new knowledge?

. Experimental evidence requires publishing, peer reviewing, validation and acceptance