c01 physical quantities, units, measurement Flashcards
What are the 7 base quantities?
Length(m), mass(kg), time(s), electric current(A), thermodynamic temperature(K), amount of substance(mol) and luminous intensity(cd)
What are the prefixes for SI Units?
Tera(10^12), Giga(10^9), Mega(10^6), kilo(10^3), deci(10^-1), centi(10^-2), milli(10^-3), micro(10^-6), nano(10^-9)
What is the order of magnitude of sizes?
Radius of hydrogen nucleus= 10^-15m
Size of a typical atom = 10^-10 m
Average width of human hair = 10^-4 m
Diameter of a wire = 10^-3 m
Length of chopsticks = 10^-1 m
Length of football field = 10^2
Height of mount Everest = 10^3 m
Radius of earth = 10^7 m
Distance travelled by light in one year = 10^15
Distance from the earth to andromeda galaxy = 10^23
What can you use to measure length and lenths SI Unit?
SI Unit: metres (m)
- metre rule 0.1m divisions
- measuring tape 0.1 divisions
What is parallax error?
Not positioning your eyes perpendicular to the line of reading
How can random errors be minimised?
By getting multiple results and measuring the mean value
How can systematic errors be minimized?
By calibrating equipment regularly.
How to use digital calipers and what is its precision and what can you use it for?
Used to measure internal, external diameter of depth of an object
1. Switch on digital calipers
2. Press zero button to ensure it reads zero
3. Ensure jaws are clean
4. Close jaws gently around measured object
5. Disregard the last digit because the instrument is highly sensitive, so precision is 0.1mm.
How to use digit micrometer screw gauge and what is its precision and what can you use it for?
Used to measure small object e.g eraser
1. Switch on digital micrometer
2. Press zero button to ensure it reads zero
3. Ensure anvil and spindle are clean
4. Close anvil and spindle gently around the object and measure it by turning the ratchet until you hear 3 clicks
5. Disregard the last digit, precision is 0.01 mm
What is an oscillation?
When the pendulum swings from start to start again
What is a scalar and vector quantity?
A scalar quantity is a physical quantity that only has magnitude.
A vector quantity is a physical quantity that has both magnitude and direction.
Examples of scalar and vector quantities?
Scalar: distance, speed, mass, energy, time
Vector: displacement, velocity, acceleration, force, weight
What is the definition of speed and velocity and their SI units?
Speed: distance moved per unit time
Velocity: rate of change of displacement
SI unit:m/s
