Chapter+2

2.1 Acceleration and the Force of Gravity Pg 56-57 Notes(From Cote) IMPORTANT: All bolded words are definitions from the glossary, if you do not understand the word look at the glossary for the meaning of the word Fundamental Forces 1) Gravitation (**Gravity**): most used 2) Magnetic/Electric(**Electromagnetic Force**): most used Order of strength(from greatest to least) 1) Strong Nuclear – nucleus of a atom 2) Electromagnetic – Infinite distance 3) Weak Nuclear - Atom 4) Gravitational – Infinite distance Forces: · Change object shape · Speed object up · Slow object down · Change object direction of travel · Start object moving · Stop object moving Units – Newton(N) Vector – has a direction associated - push or pull where [Forward, backward, up, down] Measure force – through the deformation of a spring (spring scale) - dial scale Hello dear Physicists. In most of my posts I will be posting very informative videos and articles. Most of them will be pretty advanced but will be able to create a better understanding of today's world. Enjoy Shrodinger's Cat: [] Different Levels of Dimension: part 1 [] part 2 [] The smallest of all and most expensive experiment of all? String Theory and something related to chapter 2 part 1(**WATCH THIS**!) [] part 2 [] part 3 [] part 4 [] part 5 [] part 6 [] part 7 [] part 8 [] part 9 [] part 10 [] part 11 []
 * 3) Strong Nuclear Force**
 * 4) Weak Nuclear Force**

CONTINUED: Free body diagrams (F.B.D) There are a few strategies you can use to draw free body diagrams:
 * Free body diagrams isolate the object completely from its surroundings
 * First draw the compass points and decide on a suitable scale
 * then draw as ketch of the object isolated form it surroundings
 * Locate, with a point, the approximate centre of the object
 * From the point, draw a force vector to represent each force acting on the object
 * Note: do NOT include forces that the object exerts on other objects

F.B.D can also be drawn to scale the length of the vectors represents the actual size of the force. A scale must be added by the drawing (1 cm = N) WE use F.B.D to be able to find the resultant forces.

Section 2.2 and 2.3 (From Ayesha)
 * __Section 2.2: Mass and the Force of Gravity__**

__Force of Gravity__ The force of attraction between two objects in the universe. Force of gravity between an object and a planet depends on: Mass always remains __constant__, but the weight can change due to the following factors: The force of gravity between two masses in the universe is directly proportional to the product of the masses and inversely proportional to the square of the distance between the centres.
 * || Mass || Weight ||
 * Definition || The amount of matter in an object || The term used to describe the force of gravity that a celestial body, as Earth, exerts on a mass ||
 * SI Unit || Kilograms (kg) || Newton (N) ||
 * Direction || No direction. || Always directed towards the center of the Earth. ||
 * Mass of planet
 * Mass of object
 * Distance between the centres of the two objects
 * Altitude: weight is greater at lower elevations, while lower at higher elevations.
 * Latitude: weight is greater at the poles and lower at the equator. The reason is the Earth’s bulging appearance at the equator due to its rotation and shape.
 * Newton’s Law of Universal Gravitation**

It can be written as: FG = Gm1m2 / d2 Where: G is the gravitational constant= 6.67 x 10-11 N.m2 / kg2 m1= mass of the Earth in kg m2 = mass of the other object in kg ∆ d = distance between the centres, in metres NOTE: What causes the tides? []

__**Section 2.3: Gravitational Field Intensity**__ __Force field:__ region of space where a force exists due to the presence of an object Example: region around a planet where gravity exists due to the planet’s mass. __Gravitational Field Intensity:__ Amount of force of gravity (weight) that the Earth exerts per unit mass of an object. The Earth’s gravitational field intensity is __9.8 N/kg [towards centre of Earth] or [down]__. The symbol for gravitational field intensity is the small letter, **g**. The amounts used to calculate the Earth gravitational field intensity by using the Newton’s law of universal gravitation are: G = 6.67 x 10-11 N. m2/kg2 Mass of Earth= 5.98 x 1024 kg Distance= 6.38 X 106 m Through the value of g = 9.8 N/kg [down], the weight or the force of gravitation on the object can be calculated by using the formula: Fg = mg
 * Force of gravity** = mass of the object x gravitational field intensity

__Gravitational Field Strength:__ (cont'd) Gravitational field intensity (g) varies over the surface of Earth due to latitude, altitude and due to density differences in the Earth. Table 2.2 Can detect large masses of greater density (mass) in crust with a gravimeter (used in mineral exploration). When we are larger distances away from the Earth, we get a rapid decrease in g. Table 2.3

Galileo investigated freely falling objects showing all objects fell (accelerated toward the Earth) at the same rate (ignoring air friction) Calculated the acceleration due to gravity by rolling balls down a ramp found it to be 32 ft/sec2 = 9.8 m/s2 acceleration due to gravity = 9.8m/s2 [down] we can use the kinetic equations to analyse the motion of free falling objects.
 * __2.4 Acceleration due to gravity__**

THESE ARE NOTES FOR CHAPTER THREE: __**3.1 Horizontal Motion and Friction**__ **__Reviewed:__** __**Kinematics:**__ -Mathematical descriptions or motion - Galileo __**New information:**__  __**Dynamics:**__ Why do things move the way they do? Friction a Force that opposes motion whenever one surface moves or tends to move with reference to another.

__**Types of Friction:**__ Vocabulary used to talk about the friction we want to occur include: Traction, Tread Etc.  __**Places where it is desired:**__ - Between us and the outside world.  __**Places where it is undesired:**__ - Moving large objects  - Internally in moving objects  __**Normal Force:**__ A supporting force acting perpendicular to the surface. (Doesn’t have to be vertical) Example a <span style="font-family: georgia,times new roman,times,serif;"> person moving down needs friction to push it up to stop from moving. <span style="font-family: georgia,times new roman,times,serif;">(Remember: Force of gravity always goes towards the center of the Earth. ) <span style="font-family: georgia,times new roman,times,serif;">__Ff varies F__ __N :__ If there is large normal force the friction force is large as well and the opposite is true. For example, if we were trying to move Mr. Cote and a student in our class we would need more force to move him than we would need to move the student. However, if Mr. Cote was on roller blades and the student wasn’t, it’d be easier to move him so there would need to be more force on the student to move them.
 * 1) <span style="font-family: georgia,times new roman,times,serif; margin-top: 0cm;">**__Sliding Friction :__** surface sliding past another.
 * 2) <span style="font-family: georgia,times new roman,times,serif; margin-top: 0cm;">__**Rolling Friction :**__ Opposes the motion of on surface rolling over another.(E.g. Tire rolling on ground)
 * 3) <span style="font-family: georgia,times new roman,times,serif; margin-top: 0cm;">__**Fluid Friction**__: Moving through a gas or liquid ( air resistance, drag)
 * 4) <span style="font-family: georgia,times new roman,times,serif; margin-top: 0cm;">Limiting Static Friction à When surfaces are __not__ sliding past. Resistance to the surface if motion.
 * 5) <span style="font-family: georgia,times new roman,times,serif; margin-top: 0cm;">__**Kinematic Friction:**__ The forces that oppose the motion of an object once it is moving.