General Physics

• If 1 inch (in) is equal to 2.54 centimeter (cm), how many centimeters are there in 12 inches?

  Solution

  
• Determine the area of a 6 inch x 4 inch index card.

  ans

  
• A man walked 3 meters East and then walked 3 meters West. What is the man’s displacement? What is the total distance covered by the man? Is displacement and distance the same?

  No, they are not the same.

  
• Differentiate between a scalar and a vector.

  A vector is a quantity having both magnitude and direction while a scalar is a

  quantity having magnitude only. (Note: Magnitude has a number and a unit.)
• Determine the displacement (magnitude and direction) of a car that traveled

  3 kilometer East and then 5 kilometer North.

  answer

  
• Express 300000000 meter/second in scientific notation.

  300000000 m/s = 3.00000000^ m/s = 3 x10^8 m/s
• Express 1.6 x 10^−19 Coulomb as a decimal number.

  ans

  
• Ignoring the effect of air resistance, which will fall faster from a height of 5 meters? A piece of rock? Or a feather?

  ans

  
• a form of energy that arises due to the existence of electric charges

  Electricity/electrical energy
• Electricity refers to the transmission of electrical energy through the movement of charged particles
• Electricity can exist as static electricity and current electricity
• Static electricity charges at rest (charges that are nearly stationary), cannot do work, and produced by friction, contact and induction. It is the accumulation of charges.
• Current electricity charges in motion, can do work, produced by batteries and

  generators and has two types: alternating current (ac) and direct current (dc). It is also dynamic.
• Democritus theorized that matter was made of small pieces. Leucippus introduced the term atom (atomon), which meant "indivisible" in Greek.
• The basic facts to know about the atom are that it is made up of three basic

  subatomic particles: 1) electrons (negative charge) that spin in shells around a

  nucleus that consists of 2) protons (positive charge) and 3) neutrons (neutral

  charge).
• Generally, the number of protons and electrons balance out to make the atom

  have an electrically neutral charge.
• Electrons that are farthest away from the nucleus of an atom (valence electrons) are the ones that are most easily shared with or transferred to other atoms.
• The atoms that are missing an electron or share an additional electron are called ions and combine easily with other ions to make molecules.
• The number of protons in an atom is called the atomic number. This number determines the element of the atom.
• The unit of electric charge is q.
• 1 elementary charge e = equal in magnitude to the charge on the proton or the charge of one electron.

  
  

  For example:

  • q = -5e (charge on 5 electrons)
  • q = +3e (charge on 3 protons)
  • q = 0 (charge on 2 neutrons)
• 1 coulomb C = 6.25 x 10^18 elementary charges
• Find the equivalent to elementary charge (e):

  1. q = 4 C
  2. q = 0.5 C

  ans

  
• Conductor is a material that allows charges to flow easily. Most metals are conductors: silver, gold, copper, aluminum, brass, iron, lead.
• Insulator is a material that does not allow charges to flow. Examples are plastic, wood, glass, wool, cork, rubber, air, foam.
• Electric charge can neither be created nor destroyed. It can only be transferred from one system to another.
• The material which provides transfer of charge is called conductor.
• It is a basic way to transfer a charge. Friction is done by rubbing two insulators, this is charging through this.
• Charles Augustine de Coulomb (1736-1806) is a French Physicist who formulated the Coulomb’s law which states that:

  “The electrostatic force between two charges is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance between the centers of the charges.”
• What is the formula for electrostatic force (Fe)?

  Coulomb’s Law: The electrostatic force, Fe, between two charges q1 and q2

  separated by a center-to-center distance r:

  
• What does the following means?

  • K
  • q1 and q2
  • r

  ans

  
• FE is attractive if the charges are “opposite” and repulsive if the charges are “like”.
• FE is much stronger than the gravitational force because k is much greater than G.
• FE is an “action-at-a-distance” force.
• Electrical force (Fe) can be attractive or repulsive. It is directly proportional to the charges and inversely proportional to the distance between the charges. It is very strong because K = 9 x 10^9 Nm^2/C^2 is large.
• Distance is how far an object moves or the change in position of an object.
• To find the distance or change in position, we substract the final position to the initial position, with the unit of meter.
• Scalars are quantities with magnitude (size) only. For example, the distance is 2.0 meters (magnitude).
• Vectors are quantities with magnitude and direction. For example, the displacement is 2.0 m (distance), to the west (direction).
• Distance d is a scalar. While displacement d is a vector.