Summary: Episode 25: Doctor Dan does an expose on how his Physics knowledge has stayed strong for so long! Listen to the podcast to learn who she is... MCAT Physics Vectors Scalar quantities, such as temperature, have magnitude only and are specified by a number with a unit, 67 degrees Celsius and obey the rules of ordinary algebra. Vectors, such as displacement, have both magnitude and direction, six meters west and obey the special rules of vector algebra. X and Y Coordinates Two vectors A and B may be added geometrically by drawing them to a common scale and placing them head to tail. The vector connecting the tail of A to the head of B is the sum vector. To subtract B from A, reverse the direction of B and then add to A. The component AX and AY of any vector A are the perpendicular projections of A on the coordinate axes. Pythagoras' theorem Analytically, the components are given by AX=A (cos theta) and AY=A (sine theta). Given the component, we can reconstruct the vector from: A is given by the square root of the quantity, AX2 + AY2, which is a derivation of the Pythagoras' theorem. Kinematics The motion of a body is described by giving its position or displacement, its velocity and its acceleration. The average speed is defined as the distance traveled divided by the elapsed time. The average velocity is the displacement vector divided by the elapsed time. Displacement Displacement is the vector representing the position of an object relative to its position at some chosen earlier time, or its point of origin. Whereas speed is a scalar quantity, velocity is a vector. The instantaneous velocity whose magnitude is the same as the instantaneous speed is the average velocity taken over an indefinitely short period of time. Acceleration Velocity as well other qualities describing motion are always measured with respect to some frame of reference. Acceleration is the rate of change of velocity. The change of velocity divided by the elapsed time, it is a vector. If an object moves in a straight line with constant acceleration, the velocity, V, and the acceleration, A, are related to the initial velocity V0 and the displacement, D, and the time, T, by the equations-V=V0 + AT; D, the displacement, equals V0T + ½AT2; V2=V02 + 2AD. The mean velocity equals V + V0/2. Objects allow to fall freely without air resistance all fall with the same constant acceleration, G=9.8 meters/second2. Motion and force. Newton's 3 Laws Number 1 Newton's three laws of motion are the basic laws explaining motion. Newton's first law states that if the net force on an object is zero, the object at rest remains at rest and an object in motion remains in motion in a straight line with constant velocity. The tendency of a body to resist a change in motion is called inertia. Mass is a measure of inertia. Weight refers to the force of gravity on an object. Number 2 Newton's second law states that the acceleration of a body is directly proportional to the net force acting on it and inversely proportional to its mass. F=ma, where F is the force, m is the mass, and A, the acceleration. Force, which is a vector, is a push or a pull. More precisely, Newton's second law can be used as a definition of force as that action which is capable of accelerating an object. Net force refers to the vector sum of all forces acting on a body. The force of gravity acting on a body is the product of its mass times the acceleration of gravity. Number 3 Newton's third law states that when every one body exerts a force on a second body, the second exerts an equal force on the first in the opposite direction. A consistent set of units must always be used when making calculations. SI unit s are the standard ones used for scientific work and these include the meter, kilogram and second. Friction When two bodies are in contact or slide over one another, the force of friction each exerts on the other can be written forc
