MEASUREMENT

Question 1

Define physical quantities

Answer 1

quantities that can be measured. it consists of a numerical magnitude and unit.

Question 2

precision:-

Answer 2

smallest unit a instrument can measure

Question 3

how to avoid parallax error

Answer 3

ensure that the line of sight is perpendicular to the reading

Question 4

Describe how to use a vernier calliper

Answer 4

1. grip the object using the jaws of the calliper.
2. read the main scale reading, to the immediate left of the zero on the vernier scale.(0.1cm)
3. read the vernier scale mark that coincides with the main scale mark.(0.01cm)
4. 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)

Question 5

precision of metre rule

Answer 5

0.1cm

Question 6

precision of vernier calliper

Answer 6

0.01cm

Question 7

precision of micrometer screw gauge

Answer 7

0.001cm

Question 8

describe how to use micrometer screw gauge

Answer 8

1. turn the thimble till the object is securely tightened between the anvil and spindle.
2. turn the ratchet, till it clicks
   (- indicates that the grip of screw gauge is just right to measure)
3. Read the main scale reading to the immediate left of the edge of the thimble scale.(0.1cm)
4. read the thimble scale that coincides with the datum line. of main scale (0.001cm)
5. add the two readings
   (ensure to check for zero error)

Question 9

SI unit of length

Answer 9

metre (m)

Question 10

SI unit of mass

Answer 10

kilogram kg

Question 11

SI unit of time

Answer 11

seconds s

Question 12

SI unit of luminous intensity

Answer 12

candela cd

Question 13

SI unit of electric current

Answer 13

ampere A

Question 14

SI unit of thermodynamic temperature

Answer 14

kelvin K

Question 15

SI unit of amount of substance

Answer 15

mole mol

Question 16

prefix and suffix

Answer 16

giga, mega, kilo, deci, centi , milli , micro , nano

Question 17

instrument used to measure time

Answer 17

digital stopwatch

Question 18

time in stopwatch is recorded to _____
and why

Answer 18

1 d.p. (due to human reaction time)

Question 19

define oscillation of simple pendulum

Answer 19

one complete to-and-fro motion

Question 20

define period of a pendulum

Answer 20

time taken for the pendulum to make one complete oscillation

Question 21

period of pendulum depends on length of string and mass of bob

Answer 21

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

Question 22

to calculate the time period of a pendulum, why is the time taken for 20 oscillations and not one?

Answer 22

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

Question 23

systematic error

Answer 23

an error that tends to shift all the measurements in a systematic way so that their mean value is displaced

Question 24

sensitivity of instrument

Answer 24

ability of an instrument to detect a small physical change

Question 25

advantage of taking a few readings when measuring the diameter of the wire

Answer 25

the diameter of wire may not be uniform throughout its length. by taking a few readings the average of its diameter can be obtained

Question 26

describe an experiment to calculate the time period of a simple pendulum.

Answer 26

1. Tie a mass of xg to a string, and tie it to a clamp of a retort stand. 2. pull the mass 30 degrees to the left, and let go 3. Let the string swing a few oscillations till a steady rate of swinging is reached. 4. When the string reaches the maximum displacement to the left, start the stopwatch 5. Record the time taken, t1/s for the pendulum to complete 20 oscillations 6. repeat step 5 to obtain another reading of the time taken to complete 20 oscillations, t2/s 7. calculate the t avg/s = t1 +t2/2 s 8. calculate the time period T = tavg/20