MEASUREMENT Flashcards
Define physical quantities
quantities that can be measured. it consists of a numerical magnitude and unit.
precision:-
smallest unit a instrument can measure
how to avoid parallax error
ensure that the line of sight is perpendicular to the reading
Describe how to use a vernier calliper
- grip the object using the jaws of the calliper.
- read the main scale reading, to the immediate left of the zero on the vernier scale.(0.1cm)
- read the vernier scale mark that coincides with the main scale mark.(0.01cm)
- add the two values
(ensure to check for zero error:- does the zero mark on the main scale coincide with the zero mark on the vernier scale)
precision of metre rule
0.1cm
precision of vernier calliper
0.01cm
precision of micrometer screw gauge
0.001cm
describe how to use micrometer screw gauge
- turn the thimble till the object is securely tightened between the anvil and spindle.
- turn the ratchet, till it clicks
(- indicates that the grip of screw gauge is just right to measure) - Read the main scale reading to the immediate left of the edge of the thimble scale.(0.1cm)
- read the thimble scale that coincides with the datum line. of main scale (0.001cm)
- add the two readings
(ensure to check for zero error)
SI unit of length
metre (m)
SI unit of mass
kilogram kg
SI unit of time
seconds s
SI unit of luminous intensity
candela cd
SI unit of electric current
ampere A
SI unit of thermodynamic temperature
kelvin K
SI unit of amount of substance
mole mol
prefix and suffix
giga, mega, kilo, deci, centi , milli , micro , nano
instrument used to measure time
digital stopwatch
time in stopwatch is recorded to _____
and why
1 d.p. (due to human reaction time)
define oscillation of simple pendulum
one complete to-and-fro motion
define period of a pendulum
time taken for the pendulum to make one complete oscillation
period of pendulum depends on length of string and mass of bob
false, it only depends on length and not mass
lenth is directly proportional to the square of time period
as lenth increases, the period increases but not linearly
to calculate the time period of a pendulum, why is the time taken for 20 oscillations and not one?
when the time taken is divided by 20, the inaccuracy of T associated with human reaction time will only be 1/20 of human reaction time.
thus to increase the accuracy of T calculated
systematic error
an error that tends to shift all the measurements in a systematic way so that their mean value is displaced
sensitivity of instrument
ability of an instrument to detect a small physical change
advantage of taking a few readings when measuring the diameter of the wire
the diameter of wire may not be uniform throughout its length. by taking a few readings the average of its diameter can be obtained
describe an experiment to calculate the time period of a simple pendulum.
- Tie a mass of xg to a string, and tie it to a clamp of a retort stand.
- pull the mass 30 degrees to the left, and let go
- Let the string swing a few oscillations till a steady rate of swinging is reached.
- When the string reaches the maximum displacement to the left, start the stopwatch
- Record the time taken, t1/s for the pendulum to complete 20 oscillations
- repeat step 5 to obtain another reading of the time taken to complete 20 oscillations, t2/s
- calculate the t avg/s = t1 +t2/2 s
- calculate the time period T = tavg/20
