Phys1-Mod1-1.04

Lesson "Physical Measurements."

Physical quantities

Properties of materials or substances that can be quantified by measurements.

6 prefix multipliers for metric units

1. Kilo- thousand

2. Hecto- hundred

3. Deca- ten

4. Deci- tenth

5. Centi- hundredth

6. Milli- thousandth

Distance

The length between objects.

Time

How long it takes for an event to occur.

Mass

The amount of matter in an object.

Matter

Physical substance that occupies space.

Temperature

The degree of heat present in a substance or object.

Derived units

Units calculated from the measurement of other units.

SI

The International System of Units; the main standard for measurement used in science.

7 SI base units

1. Meter (m)- length

2. Kilogram (kg)- mass

3. Second (s)- time

4. Ampere (A)- electric current

5. Kelvin (K)- temperature

6. Mole (mol)- amount of substance

7. Candela (cd)- luminous intensity

How do you properly measure objects/read a scale (estimation)?

Estimate one decimal place past the smallest graduation.

Percent error

How far an experimental (measured) value is from an accepted (true) value, expressed as a percentage.

Percent error formula

$$\frac{\vert Experimentalvalue-Acceptedvalue\vert}{Acceptedvalue}\cdot100$$

Significant figures

The digits in a number that carry reliable meaning regarding its precision or accuracy.

Sigfig rules

• Nonzero digits, captive zeros, zeroes to the right of a decimal point are significant, and all digits in the coefficient of a number in scientific notation are significant.

• Leading zeros are not significant.

• Sigfig rules apply to measurements and constants (which usually come from measured values), but not counting numbers (integers).

Sigfig rules in calculations

• Adding or subtracting numbers: Round the result to the same number of decimal places as the number with the least number of decimal places.

• Multiplying or dividing numbers: Round the result to the same number of digits as the number with the least number of significant figures.

• *If the digit to be dropped (the one immediately to the right of the digit to be retained) is less than 5, "round down" and leave the retained digit unchanged; if it is more than 5, "round up: and increase the retained digit by 1. If the dropped digit is 5, and it’s either the last digit in the number or it’s followed only by zeros, round up or down, whichever yields an even value for the retained digit. If any nonzero digits follow the dropped 5, round up.

Counting numbers

Positive whole numbers.

Integers

All whole numbers, both positive and negative, including zero.

Constant

A fixed value that never changes.

Scalar quantities

Quantities that can be described completely by their magnitude. Scalar quantities include distance, speed, mass, and time.

Vector quantities

Quantities that require both a magnitude and direction for a complete description. Vector quantities include displacement, velocity, acceleration, force, and momentum.

Magnitude

Size or amount.