1. Physical Quantities and Units

Question 1

What is a physical quantity?

Answer 1

A physical quantity is a quantity that can be measured.

Question 2

What are the constituents of a physical quantity?

Answer 2

A physical quantity consists of numerical magnitude (value) and a unit.

Question 3

What is the SI base unit for mass?

Answer 3

The SI base unit for mass is the kg - kilogram.

Question 4

What is the SI base unit for length?

Answer 4

The SI base unit for length is the m - metre.

Question 5

What is the SI base unit for time?

Answer 5

The SI base unit for time is the s - second.

Question 6

What is the SI base unit for current?

Answer 6

The SI base unit for current is the A - Ampere.

Question 7

What is the SI base unit for Temperature?

Answer 7

The SI base unit for temperature is K - Kelvin.

Question 8

What causes Random Errors in measurements?

Answer 8

Random Errors when taking measurements, are a result of uncontrollable factors; such as environmental conditions.

Question 9

How do Systematic Errors arise when taking measurements?

Answer 9

When taking measurements, Systematic Errors arise from the use of faulty instruments or from flaws in the experimental method.

Question 10

Explain the effects of Random Errors when taking measurements.

Answer 10

Random Errors when taking measurements, produce an effect on the Precision of the measurements taken, resulting in a wider spread of values about the mean value.

Question 11

Explain the effects of Systematic Errors when taking measurements.

Answer 11

Systematic Errors when taking measurements result in the readings produced being on either side of the true value; either greater or less than the true value. This is due to the Accuracy having been affected.

The effect on accuracy is because the error is repeated every time the intstrument or techniques is used.

Question 12

How are Random Errors reduced?

Answer 12

Random Errors are reduced by repeating measurements several times and calculating an average from them.

Question 13

How are Systematic Errors reduced?

Answer 13

Systematic Errors, when taking measurements, are reduced by recalibrating instruments, or correcting and/or adjusting the technique applied.

Question 14

What is precision, when taking measurements?

Answer 14

When taking measurements, Precision, is how close the measured values are to each other.

If a measurement is repeated, they are described as precise when they are very similar, or the same as each other.

Question 15

What is accuracy, when taking measurements?

Answer 15

When taking measurements, Accuracy, is how close a measured value is to the true value.

This can be increased by repeating measurements and finding an average

Question 16

What is the uncertainty in a reading, when taking measurements?

Answer 16

When taking measurements, the uncertainty in a Reading is ±half the smallest division.

Question 17

What is the uncertainty in a measurement, when taking measurements?

Answer 17

When taking measurements, the uncertainty in a measurement is ± at least 1 the smallest division.

Question 18

What is the uncertainty in repeated data, when taking measurements?

Answer 18

When taking measurements, the uncertainty in repeated data is ± half the range

Question 19

What is the uncertainty in digital readings, when taking measurements?

Answer 19

When taking measurements, the uncertainty in digital readings is ± the last significant digit unless otherwise qouted.

Question 20

What is the maximum uncertainty when taking measurements?

Answer 20

When taking measurements, the maximum uncertainty is ± half the smallest division.

Question 21

How are uncertainties combined in addition and subtration?

Answer 21

In addition and subtraction, uncertainties are ALWAYS added together.

These are the uncertainties of the involved terms.

Even in addition, uncertainties are only added.

Question 22

What is the formula for the combining of uncertainties in addition and subtraction?

Answer 22

dx = dy + dz

Where these are absolute uncertainties.
**Uncertainties are always ADDED

Absolute values =
x = y + z
or
x = y - z

Question 23

What is the absulute uncertainty?

Answer 23

The absolute uncertainty is the actual uncertainty of a number. That is, Absolute uncertainty is dx in x±dx.

Question 24

What is the formula for the calculation of fractional uncertainty?

Answer 24

The formula for fractional uncertainty is:
Fractional Uncertainty = Absolute uncertainty / True value

i.e dx/x

Question 25

What are the 7 Base Quantities? | Quantities from which every other can be derived.

Answer 25

The 7 base quantities are: 1. Mass 2. Length 3. Time 4. Current 5. Temperature 6. Amount of substance 7. Light intensity | Knowledge of the first 5 is necessary according to the syllabus.

Question 26

When is an equation homogeneous?

Answer 26

An equation is homogeneous if all the terms have the same base units. ## Footnote As a result it is checked by expressing all the terms in an equation in terms of their base units, which, **are displayed in square brackets**

Question 27

If an equation is not homogeneous it is wrong/incorrect. However, an equation can be homogeneous but still be incorrect due to what?

Answer 27

An equation can still be incorrect even while it is homogeneous due to: 1. Addition of an extra (incorrect term) 2. Elimination of (necessary) terms 3. Wrong coefficient ## Footnote Experiments were done to check for and get accurate equations.

Question 28

What is the multiplying factor of the prefix, Tera-, symbol, T?

Answer 28

The multiplying factor of the prefix, Tera-, is **10¹²**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 29

What is the multiplying factor of the prefix, Giga-, symbol, G?

Answer 29

The multiplying factor of the prefix, Giga-, is **10⁹**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 30

What is the multiplying factor of the prefix, Mega-, symbol, M?

Answer 30

The multiplying factor of the prefix, Mega-, is **10⁶**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 31

What is the multiplying factor of the prefix, kilo-, symbol, k?

Answer 31

The multiplying factor of the prefix, kilo-, is **10³**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 32

What is the multiplying factor of the prefix, deci-, symbol, d?

Answer 32

The multiplying factor of the prefix, deci-, is **10⁻¹**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 33

What is the multiplying factor of the prefix, centi-, symbol, c?

Answer 33

The multiplying factor of the prefix, centi-, is **10⁻²**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 34

What is the multiplying factor of the prefix, milli-, symbol, m?

Answer 34

The multiplying factor of the prefix, milli-, is **10⁻³**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 35

What is the multiplying factor of the prefix, micro-, symbol, µ?

Answer 35

The multiplying factor of the prefix, micro-, is **10⁻⁶**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 36

What is the multiplying factor of the prefix, nano-, symbol, n?

Answer 36

The multiplying factor of the prefix, nano-, is **10⁻⁹**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 37

What is the multiplying factor of the prefix, nano-, symbol, n?

Answer 37

The multiplying factor of the prefix, nano-, is **10⁻⁹**. ## Footnote To add a prefix to an SI unit, we divide by the multiplying factor.

Question 38

Define the distinction between accuracy and precision.

Answer 38

Accuracy is how close the results are to the true value while precision is how close results are to each other. ## Footnote A dart hitting the bullseye is accurate, but if the rest of the darts thrown are not close to the bullseye, they are not only less accurate than the first dart thrown, but they are also imprecise. At the same time, a group of darts may be nucleated around an inaccurate region but with all the darts close together, the group of darts is precisely thrown. - Genetally, however, both would be desired in any experiment or activity requiring them.

Question 39

What is the formula applied in the combining of uncertainties in which the values in question are multiplied of divided.

Answer 39

du/u = dx/x + dy/y + dz/z | In this case, division, or multiplication: ADD FRACTIONAL UNCERTAINTIES. ## Footnote x, y, and z are the values that were added or subtracted. u is the result of x, y and z. the d added to each letter, eg. du, together with the letter itself, represent the uncertainties of the values.

Question 40

What is the rule pertaining to constants and powers, when dealing with finding the uncertainties of derived values? [2]

Answer 40

The rule pertaining to constants and powers, when dealing with finding the uncertainties of derived values is that: **The constant of a value is not considered when calculating uncertainties, however, when a value, x, is to the power a, a becomes a constant to the fractional uncertainty of x, that is, adx/x. **

Question 41

What is the formula for the percentage uncertainty of a value?

Answer 41

Percentage uncertainty = **absolute uncertainty(dx)/True value(x) x 100** | or just FRACTIONAL UNCERTAINTY x 100

Question 42

How are vector quantities different from scalar quantities?

Answer 42

Vector quantities are different from scalar quantities in that they have both magnitude and direction, while scalar quantities have only magnitude.

Question 43

Give 5 examples of Vector quantities.

Answer 43

5 examples of vector quantities are: 1. Velocity 2. Displacement 3. Momentum 4. Force 5. Acceleration

Question 44

Give 5 examples of Scalar quantities.

Answer 44

5 examples of Scalar quantities are: 1. Distance 2. Speed 3. Energy 4. Time 5. Temperature

Question 45

What are two methods of adding or subtracting coplanar vectors?

Answer 45

Two methods of adding or subtracting coplanar vectors are: 1. Calculation method 2. Measuring - Scale diagram ## Footnote The Calculation method includes, Parallelogram diagram or Vector triangle diagram.

Question 46

How is a vector represented as two perpendicular components? ## Footnote **NOTEBOOK = IN DEPTH + CALCULATION + APPLICATION**

Answer 46

This is done by resolving the perpendicular components of a resultant vector. It includes finding the horizontal and vertical forces contributing to the resultant force at an angle. ## Footnote This can only be done for a vector at an angle, not 90° or 0°. It's like working in reverse from the resultant to the components that it is made up of.

Question 47

What formula is used to resolve the horizontal component of a force?

Answer 47

Fₕ = FCosθ ## Footnote F - resultant force, at an angle Fₕ - horizontal component of F θ - The angle below the line representing F Remember cos is like close... imagine a laptop This can be Sinθ when you subtract the angle under the line representing F from 90 degrees, and use that angle, that is, the upper angle.

Question 48

What formula is used to resolve the vertical component of a force?

Answer 48

Fᵥ = FSinθ ## Footnote Fᵥ - vertical component of F F - resultant force, at an angle θ - The angle below the line representing F This can be cosθ when you subtract the angle under the line representing F from 90 degrees, and use that angle, that is, the upper angle.