Sarah+Roper

//__Relative Motion__// How many metres is each car travelling towards each other in a second? 90 000m ÷ 3 600 = 25ms¯¹ 25ms¯¹ x 10 = 250m (to overtake car). 100 000 ÷ 3 600 = 27.777…ms¯¹ 27.777…ms¯¹ x 10 = 277.777…m (car coming in opposite direction). 277.777… + 250 > 500m Therefore, because the car opposite is travelling too quickly, it is not safe to overtake the car. __//Newton’s contributions to Physics//__ //__Newton’s Universal Law of Gravitation__//
 * 14/2/12**
 * Question 1:** Two trucks are travelling towards each other on the freeway (see figure). The larger truck, C, is travelling east at 60 km h-1, and the smaller truck, D, is travelling west at 100 km h-1. What is the velocity of C relative to D?
 * 160kmh¯¹ due west.**
 * Question2:** Consider two cars, X and Y, travelling towards each other at 27.78 m s-1. What is the velocity of X relative to Y?
 * 55.56s¯¹ due the direction X is travelling in.**
 * 55.56 metres.**
 * Question 3:** Two cars pass each other, the first travelling 30.5 m s-1 north, the second at 25 ms-1 south. Find the velocity of the second car relative to the first.
 * 55.5ms¯¹ due north.**
 * Question 4:** What is the relative velocity of a fielder to a cricket ball if the ball is moving south at 12 ms-1 and the fielder north at 5 ms-1?
 * 17ms¯¹ due north.**
 * Question 5:** Imagine you are in a car that has to travel at 90 km h-1 to overtake a slower car. To do this will take you 10 seconds. However there is another car travelling towards you at 100 km h-1 at a distance of 500m. Can you overtake the slower car safely?
 * 15/2/12**
 * Discovered the binomial theorem and developed the calculus that employs infinite considerations in finding the slopes of curves and areas under curves.
 * Developed the law of universal gravitation.
 * Established the three laws of motion.
 * Uncovered new aspects of science and mathematics that moved eighteenth century progress forward.
 * He used advanced mathematics to develop new, refined calculations that benefited eighteenth century work.
 * Defined nature and inspired deism (a theology that God is observable only through the physical laws of the universe).
 * States that the force of gravity between two objects is equal to the universal gravitational constant multiplied by the mass of each object, divided by the square of the distance between the two objects.
 * **F = G(m****₁m₂ ÷ r****²****)**
 * The gravitational force is proportional to the product of their masses, so as the product increases so does the gravitational force (and vice versa).
 * The force is inversely proportional to the square of the distance, thus as the distance increases, the gravitational force decreases (and vice versa).
 * Newton’s laws of motion, together with his law of universal gravitation and the mathematical techniques of calculus provided for the first time a unified quantitative explanation for a wide range of physical phenomena.

- Newton’s First Law of Motion states that //an object at rest will remain at rest, and a moving object stays at a constant speed without changing direction, unless an unbalanced outside force acts on it.// - On earth, a stationary has at least two balanced forces. These are the //gravitational force// (weight) and the //supporting force// of the surface it rests on. - If the net force is 0 the velocity is constant. - When an object moves it experiences a frictional force that tends to slow it down. It needs a forward force to keep it moving at a constant speed. - Inertia is the tendency of a mass to resist changes in motion. - Newton’s First Law of Motion is also known as the Law of Inertia. - Newton’s Second Law of Motion states that //when a net force acts on an object it produces an acceleration that is proportional to the size of the force.// - Acceleration is the change in velocity of an object. - **Force = mass x acceleration**. - Newton’s Third Law of Motion states //when one object exerts a force on a second object, then the second object exerts a force on the first object in the opposite direction.//
 * 17/2/12**


 * **Year** ||  **Person**  ||  **Contributions to the concept of gravity**  ||
 * 6th Century B.C.E || Anaximander || * Believed that the earth was a disk in the centre of the universe, that the fires of hell burnt within it, and the vault of heaven was stretched above the earth. Holes through the vault uncovered more fires which were known as ‘stars’. ||
 * 2nd Century C.E. || Claudius Ptolemy || * Saw the earth as the centre of the universe where the sun, planets and moon were attached to solid, transparent spheres.
 * Allowed astronomers to make fairly accurate predictions regarding ellipses of the sun and moon and future positions of the planets. ||
 * 16th Century C.E. || Nicholas Copernicus || * Opposed the idea that the earth was the centre of all things.
 * Proposed that the planets revolved around the sun. ||
 * 17th Century C.E. || Johannes Kepler || * Refined the Copernican model.
 * Established the orbits of planets were not perfect circles, but ellipses.
 * Discovered that the planets moved faster as they came closer to the sun. ||
 * 1643 || Isaac Newton || * Developed a mathematical prove of planetary forces.
 * Three laws of motion.
 * Showed that the moon could only maintain its elliptical orbit if it was attracted to the earth.
 * Claimed centrifugal forces prevented the moon from clashing into the earth.
 * Proved mathematically that centrifugal force and gravity keep the planets in orbit.
 * Formulated the Universal Law of Gravity.
 * Explained the reasons behind earth tides.
 * Recognised that white light was made up of the colours of the spectrum.
 * Introduced the concept of light diffraction. ||
 * 1879 || Albert Einstein || * Proved that gravity exerted an influence on time. ||

**29/2/12** **//Social Implications of Collisions//** Aside from the obvious physical and emotional strain a collision can impose on an individual, the effect on the community can indeed be significant. A road vehicle collision, whilst in itself sparks concern and apprehension for onlookers in regards to the welfare of accident victims, can place enormous pressure on a community’s financial and economic situation. Depending on the extremity of the accident, the cost to repair infrastructure can vary, and yet if a vehicle was to uncontrollably launch into a nearby yard the expense would fall on the residents. A collision can potentially endanger the lives of close pedestrians, irrefutably adding medical costs to the list. The general mood and morale of the community would be at its lowest, particularly for those who have personally suffered, either it being physical, emotional or psychological. Traffic would be horrendous. Congestion is next to impossible to avoid in the event of a road vehicle collision, which could place immediate stress on surrounding residents. A medical emergency i.e. having a baby could potentially sound disaster. The increasing road traffic could in all probability slow down the ambulance, widening the prospect of medical problems. The media attention for the collision would also be a continuous issue for close neighbours, and act as a course for constant annoyance. **1/3/12** The points listed below were the safety measures taken in a collision experiment to ensure the protection of an egg. //Seatbelt// – the seatbelt (a rubber band stretched diagonally across the egg) was attached securely to the trolley seat which, upon impact with the wall, stopped the egg from launching forward, and if unsecure would have been responsible for the inevitable crash and splatter of egg yolk. Newton’s First Law of Motion, the Law of Inertia, states that an object with remain at a constant speed unless an external unbalanced force acts upon it. The external unbalanced force in this experiment was the seatbelt, which prohibited the egg’s motion, therefore preventing yolk spillage. //Cushion// – the egg was surrounded by a cushion (cotton wool) to prevent the egg from damaging itself against the hard surface of the trolley whilst in motion. The egg was successfully saved in all three collision trials, and did not crack for it was well protected. //Box// – a box (made of newspaper) was folded to contain the egg and prevent it from falling off the sides of the trolley whilst in motion. If the egg was not contained, the sudden impact with the wall would have caused the egg to continue at its previous state of motion and fly into the wall. However the box, along with the seatbelt, acted as external forces and therefore halted the egg’s motion. **2/3/12** - The magic of a swing comes from the rhythmic change that is momentarily stopped high up off the ground and swooped back down again at an increasing speed. - As the swing rises again and slow down, the kinetic energy is spent so the swing is stopped (//kinetic → potential → kinetic//). - Height and velocity cannot happen simultaneously. - Transference of energy from two people to one person gives twice the height. - Some energy in the transference of energy is lost to friction. - Roller coasters rely on potential energy at the beginning of the ride (//potential → kinetic → potential//). - Some energy becomes heat due to frictional forces. - **Terminal velocity** is the maximum speed of an object. - Work = force x distance - When going up the distance is //h// and the force is //mg//. - When going down (mg x h = friction x slide). - Work is done when energy is converted. - Mgh = force x distance - With four people on a tight rope, fg = 4mg (less sag higher tension). - Anything that is thrown is called a **missile** and the path it follows is the **trajectory**. - Depending on the horizontal velocity of a freefalling flying object a variety of parabolas can be formed. - Parabolas (y = -mx²).

**12/3/12** __What is a GPS?__ A //GPS// or Global Positioning System is an electronic receiver of global navigational satellite signals to determine the precise location and velocity of an object. It also provides global time synchronisation for land, air and sea travel. The satellite-based navigation system is made up of a network of 24 satellites placed into orbit by the U.S. Department of Defence. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works through any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. __Describe the operation of a GPS.__ GPS satellites circle the earth twice in the course of a day in a very precise and synchronised orbit. They transmit signal information to earth, whereby GPS receivers absorb this information, using triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal transmission from the satellite relays the time it was received. The time difference tells the GPS receiver how far away the satellite is. With further distance measurements from several satellites, the receiver can determine the user's position and display it on the unit's electronic map. A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.