General Physics 1 – Units, Physical Quantities and Measurements

Vocabulary flashcards summarizing essential terms from the lecture on units, measurement, significant figures, errors, and uncertainty.

Measurement

Process of comparing a physical quantity with a standard unit to determine its value.

Standard Unit

A fixed, reproducible value used for accurate measurements.

British (English) System

System of units (foot-pound-second) still widely used in the United States.

Metric System

Decimal-based system of units used in most of the world (meters, grams, etc.).

International System of Units (SI)

Modern form of the metric system agreed upon globally for scientific measurement.

Fundamental Quantity

Basic physical quantity independent of others (e.g., meter, kilogram, second).

Derived Quantity

Physical quantity formed from combinations of fundamental quantities (e.g., speed, work).

Significant Figures (SF)

Digits in a measured number that convey meaningful information about its precision.

Leading Zeros

Zeros to the left of the first non-zero digit; not significant.

Trailing Zeros (with decimal)

Zeros at the end of a number with a decimal point; significant.

Exact Number

Value known with infinite significant figures (e.g., defined conversions, π).

Scientific Notation

Powers-of-10 format for writing very large or very small numbers (e.g., 3.6 × 10⁵).

Unit Conversion

Changing from one unit to another using a conversion ratio equal to one.

Accuracy

Closeness of a measurement to the true or accepted value.

Precision

Closeness among repeated measurements made the same way.

Random Error

Unpredictable variation in measurement affecting precision.

Systematic Error

Consistent bias from instrument or method that limits accuracy.

Percentage Error

(Measured − True) ÷ True × 100%; indicates accuracy.

Percentage Difference

|Value₁ − Value₂| ÷ Average × 100%; indicates precision between measurements.

Variance

Average of the squared deviations from the mean; gauges spread of data.

Standard Deviation

Square root of the variance; shows dispersion of measurements around the mean.

Uncertainty

Expressed range within which the true value is asserted to lie with confidence.

Absolute Uncertainty

Uncertainty having the same units as the measurement, written ± least count.

Relative (Percent) Uncertainty

Absolute uncertainty divided by measured value, expressed as a percentage.

resultant vector

The sum of two or more vector quantities.

commutative and associative

Properties of Vector Addition

commutative

➢The order of adding vectors may be change without affecting the resultant

➢A + B= B + A

associative

➢The grouping of vectors to be added may also be changed without affecting the resultant.

➢(A + B) + C= A + ( B + C)

parallelogram and polygon

2 types of graphical method

using laws of sines and cosines and component method

2 types of analytical method

resolution of vectors

The process of splitting the vector into its components.

✓Horizontal component

✓Vertical component

Product of a vector and a scalar

Momentum, force

Dot product of two vectors

Also called scalar product

• The ______ may be positive, negative or zero depending on the angle between them

• A•B= ABcos Ꝋ

Cross product of two vectors

Also called vector product

• A x B= AB sin Ꝋ

unit vector

A dimensionless vector with a magnitude of 1.

mechanics

a branch of physics concerned with the motion of bodies under the action of forces, including the special case in which a body remains at rest.

Kinematics, Dynamics and Statics

motion is divided into 3 branches

kinematics

Describes motion in terms of displacement, velocity and acceleration.

dynamics

Is the study of force in relation to motion.

statics

which deals with forces acting on and in a body at rest

translation

term used for motion in a straight line

displacement, velocity and acceleration.

translation described by three quantities

position

The location of an object with respect to a reference point or origin

Displacement

refers to the straight-line distance between an object’s initial and final position with direction toward the final position.

distance

refers to the total length of path taken by an object in moving from its initial to final position.

Speed

the distance travelled by a body in a given time. Scalar quantity

Velocity

the rate of change of position. Vector quantity

average speed

Total distance travelled divided by the total time elapsed.

Average velocity

is displacement (change in position) divided by the time of travel

Instantaneous velocity

is the average velocity at a specific instant in time (or over an infinitesimally small-time interval).

Radio Detection and Ranging gun

Radar Gun meaning

Light Detection and Ranging gun

LIDAR Gun means

Instantaneous speed

is the magnitude of instantaneous velocity.