1.1 – Measurements in physics
1.1.1.1 Fundamental SI Unit
Physics is an experimental science. All physics measurements are expressed in units. There are hundreds different units in physics, but only 7 of them are fundamental.
The 7 fundamental units are:
Meter m, the unit of distance.
Kilogram kg, the unit of mass.
Second s, the unit of time.
Ampere A, the unit of electric current.
Kelvin K, the unit of temperature.
Mole mol, the unit of particle numbers.
One mole equals the number atoms in 12 g of carbon.
Candela cd, a unit of luminous intensity. But it is not a required in IB Physics.
The 7 fundamental units are:
Meter m, the unit of distance.
Kilogram kg, the unit of mass.
Second s, the unit of time.
Ampere A, the unit of electric current.
Kelvin K, the unit of temperature.
Mole mol, the unit of particle numbers.
One mole equals the number atoms in 12 g of carbon.
Candela cd, a unit of luminous intensity. But it is not a required in IB Physics.
1.1.1.2 Derived SI Units
Except the 7 fundamental units, all the other units are derived. Derived unit are combinations of two or more fundamental units. not a required in IB Physics.
1.1.2 Metric Multipliers and Scientific Notation
Metric multipliers are the prefixes of the units. Small or large quantities can be expressed by powers of 10.
There is a Metric multipliers table in the data booklet.
In Scientific notation, a number will be expressed in the form a × 10b, where a is a decimal which is larger equal to 1 and less than 10 (1≤ a <10) and b is a positive + or negative – integer.
In Scientific notation, a number will be expressed in the form a × 10b, where a is a decimal which is larger equal to 1 and less than 10 (1≤ a <10) and b is a positive + or negative – integer.
1.1.3.1 Significant Figures
It is a number of digits used to express a value how precisely it could be. In most of cases, the last digit in Significant figures decide the accuracy of the value.
There are 4 basic rules to find the number of significant figures:
1.Count zero between the non-zero numbers,
for example, 504, it is 3 s.f.
2.Do not count zeros at the end of an integer,
for example, 608 00, it is 3 s.f.
3.Do not count zeros in front,
for example, 0.00305, it is 3 s.f.
4.Count zeros at the end of a decimal,
for example, in this question 0.0450, it is 3 s.f.
There are 4 basic rules to find the number of significant figures:
1.Count zero between the non-zero numbers,
for example, 504, it is 3 s.f.
2.Do not count zeros at the end of an integer,
for example, 608 00, it is 3 s.f.
3.Do not count zeros in front,
for example, 0.00305, it is 3 s.f.
4.Count zeros at the end of a decimal,
for example, in this question 0.0450, it is 3 s.f.
1.1.3.2 Significant Digits in Calculation
In multiplication x or division / or in power ^ or in a root, the result must match significant figures with the least or lowest precisely value in the calculation. In addition + or subtraction -, the number of decimal digits in the answer must be equal to the least or the shortest number of decimal places in the calculation.
When writing values to the correct number of decimal places or significant figures, you have to carefully rounding the number.
When writing values to the correct number of decimal places or significant figures, you have to carefully rounding the number.
1.1.4 Orders of Magnitude and Estimates
In physics, there are many values are too big 1000000 or too small 0.000001. To express or compare or estimate those values we would like to use the “order of magnitude” which give a rough estimate what’s the value is.
The “order of magnitude” is simply expressing a quantity just as a power of 10. For example, the mass of the universe has an order of magnitude 1053 kg.
In the textbook, you can find few tables listed some of “order of magnitude” values such as distances, masses and times.
The “order of magnitude” is simply expressing a quantity just as a power of 10. For example, the mass of the universe has an order of magnitude 1053 kg.
In the textbook, you can find few tables listed some of “order of magnitude” values such as distances, masses and times.