Answer:
Speed equals distance divided by time. Its SI unit is therefore metre per second, written as m s-1.
Question 22
What are SI prefixes?
Answer:
SI prefixes are words or symbols placed before units to represent powers of ten. Examples include milli, micro, kilo, mega and giga.
Question 23
What do the prefixes milli, micro and nano represent?
Answer:
Milli represents 10-3, micro represents 10-6, and nano represents 10-9. Their symbols are m, micro symbol, and n respectively.
Question 24
What do the prefixes kilo, mega and giga represent?
Answer:
Kilo represents 103, mega represents 106, and giga represents 109. Their symbols are k, M and G respectively.
Question 25
What is scientific notation?
Answer:
Scientific notation is a compact method of writing very large or very small numbers as a number from 1 to 9 multiplied by a power of ten.
Question 26
How is a large number written in scientific notation?
Answer:
Move the decimal point to the left until one non-zero digit remains before it. The number of places moved becomes the positive exponent of 10.
Question 27
How is a small number written in scientific notation?
Answer:
Move the decimal point to the right until one non-zero digit remains before it. The number of places moved is written as a negative exponent of 10.
Question 28
State two rules for writing SI unit symbols.
Answer:
A unit symbol is not an abbreviation and does not take a plural form. Symbols are generally lowercase, except those derived from scientists names, such as N for newton and Pa for pascal.
Question 29
What is least count?
Answer:
Least count is the smallest measurement that an instrument can measure accurately. It indicates the precision available from the instrument scale.
Question 30
What is the least count of a metre rule?
Answer:
The least count of a standard metre rule is 1 mm because its smallest marked division is one millimetre.