1. The Fundamental Physical Quantities
Chapter 1
The Fundamental Physical Quantities

2. Length: spatial separation of two points
Standard unit: Meter (m)
Do not use English units (feet, inches, etc.)
The reference of a meter is the length of a metal bar kept at the International Bureau of Weights and Measures in France
Displacement: A distance that has direction and magnitude and is measured with some unit of length
Quantities that have direction and magnitude are called vector quantities

3. Derived units are obtained by combining other units:
From the unit of length, meter (m), we derive unit of area, square meter (m2), etc.
Time: it is measured with “seconds” as standard unit (sec). The reference to one second used to be the duration of a solar day divided by 24x60x60
Velocity: the rate at which the displacement of an object changes.
Displacement is a vector quantity, thus so is velocity.
The magnitude of velocity is called speed.
The unit of speed is derived from units of length and time: m/sec.
To calculate the speed, divide distance (or magnitude of displacement) by time: S=D/t
Acceleration: the rate at which velocity changes. But for our purposes we do not account for direction, and simply consider the change of speed over time
Standard unit is m/sec2

4. Mass: The amount of matter present in an object.
Standard unit: kilogram (kg)
Force: a push or a pull
It is a vector quantity.
Creates acceleration in the same direction it is applied, or deformation.
Is measured using the formula F=M.a (mass times acceleration)
Can also be measured using a spring balance or a beam balance
Standard unit is Kg.m/sec2 which is known as Newtons
Always comes in pairs: for every force there is a reaction is the opposite direction.
Multiple forces on the same object can combine and form a resultant force
Examples: gravity, friction, tension, etc.
Friction can adapt to the magnitude of the force
Forces can create equilibrium
Momentum: the tendency to preserve the velocity, unless force is applied.
A moving object at constant velocity has no force applied to it. The motion is due to its momentum.

5. Pressure: force that is applied to a surface (as opposed to a point)
Force (continued)
Gravity is the force that all matters apply to one another. Earth applies this force to every object on it. This force is proportionate to the object’s mass. Since acceleration is inversely proportionate to an object’s mass, the acceleration caused by gravity (in a free fall) is then equal among all objects of various masses. This value, which is dependent upon the mass of earth, is known as g = 9.8 m/sec2
A spring balance works by measuring the stretch on the spring
A beam balance works by equating the masses on the two pans.
Pressure: force that is applied to a surface (as opposed to a point)
Liquids and gases apply pressure to their surroundings.
Can be measured using formula p=F/A (force per area)
The unit of measurement is thus newtons per square meter (N/m2)
Sound is generated by small and quick changes in air pressure

6. Power: the rate at which work is done on an object.
Work and Energy
when force is applied to an object and accelerates it, the work done is defined as W=F.D (force times displacement)
The measurement unit thus is newton meters which is known as joules
To do work one needs to expend energy. Energy has the same measurement unit as work.
To measure amount of expended energy, measure the amount of work done.
Mechanical energy (the kind we are discussing) comes in two forms: potential energy and kinetic energy
Potential energy is stored in an object due to its configuration
A lifted weight, a string in tension, etc.
Kinetic energy is stored in an object due to its motion
The work done on an object is equal to the sum of its potential and kinetic energies.
Lifting creates potential energy
Throwing creates kinetic energy
Releasing tension or dropping will convert potential energy to kinetic.
Power: the rate at which work is done on an object.
Unit of measurement is joules per seconds (j/s) known as watt (w)
Electric companies use an alternative unit for energy using watts which is kilowatt- hour