Unit Prefixes

Here are some examples of the use of prefixes:

• 70 000 m can be written as 70 km (kilometre)

• 0, 001 g is the same as 1 × 10^−3 g and can be written as 1 mg (milligram)

• 2, 6 × 10^6 N can be written as 2, 6 MN (meganewton)

Average Speed and Average Velocity

Average Speed is the ration of distance per unit time.

• Speed is always positive.
• In the SI system, the unit of speed is the meter per second (m/s)
• In practice, the speed of automobiles, aircraft, and other everyday objects is ofteneasured in kilometers per hour (km/h):

Average Velocity is the ratio of the change of position and the time interval.

is also written as:

• In the SI system, the unit of speed is the meter per second (m/s)
•  Velocity can be positive or negative. A negative velocity refers to motion in the negative direction for the coordinate axis chosen.
• We cannot tell the velocity is positive or negative until the direction at the x-axis is specified.

Newton's Law of Motion (Law of Dynamics)

• 1st Law, Law of Inertia: In the absence of a net force, a body at rest remains at rest and a body in motion will continue in motion at constant velocity 
• 2nd Law, Law  of Acceleration: When a net force acts on a body, it will be accelerated in the direction of the force with an acceleration directly proportional to the mass. (equation of motion)
• 3rd Law, Law of Interaction: When a body exerts a force on another body, the 2nd body exerts a force on the 1st body of the same magnitude but in the opposite direction.

MULTIPLES AND SUBMULTIPLES OF THE METER

kilometer (klick) - 1 km - 103 m
meter - 1 m
centimeter - 1 cm - 10 2 m
millimeter 1 mm 10 3 m
micrometer (micron) 1 m 10 6 m
nanometer 1 nm 10 9 m
angstrom 1 Å 10 10 m
picometer 1 pm 10 12 m
femtometer (fermi) 1 fm 10 15 m

Greek Alphabet

What is the importance of wiping the ice before introducing it to water in the calorimeter?

The specific heat of water is different from the specific heat of ice and also of wet ice. If the ice is not wipe before introducing into a calorimeter experiment it can increase the mass of water in the calorimeter and become source of inaccuracy.

Atoms

Atoms are the smallest particles of  matter. Atoms cannot be divided into smaller parts without changing their  properties. Atoms have a nucleus surrounded by a cloud of electrons. 

An atom consists of a tiny dense nucleus surrounded by electrons that are spread throughout a relatively large volume of space around the nucleus. The nucleus contains positively charged protons and neutral neutrons, so it is positively charged. The electrons are negatively charged. Because the amount of positive charge on a proton equals the amount of negative charge on an electron, a neutral atom has an equal number

of protons and electrons. Atoms can gain electrons and thereby become negatively

charged, or they can lose electrons and become positively charged. However, the number

of protons in an atom does not change.

Protons and neutrons have approximately the same mass and are about 1800 times

more massive than an electron. This means that most of the mass of an atom is in its

nucleus. However, most of the volume of an atom is occupied by its electrons, and that

is where our focus will be because it is the electrons that form chemical bonds.