Several themes are recurrent Themes for GEOG/PHYS 182: Force Energy Field Equilibrium Diffusion

Force Force – Any interaction that tends to change the motion of an object. -Intuitively a push or pull Four types of fundamental forces: Gravitational Electromagnetic Weak Strong (Nuclear) SI unit of force: N (newton)

Newton’s Laws of Motion Newton’s first law: A moving object will continue moving in a straight line at a constant speed, and a stationary object will remain at rest, unless acted on by an unbalanced force. Newton’s second law: The acceleration produced on a body by a force is proportional to the magnitude of the force and inversely proportional to the mass of the object. Newton’s third law: For every action there is an equal and opposite reaction. for two bodies, A and B

Work and Energy Energy – A property of objects, transferrable among them via fundamental interactions, which can be converted into different forms, but not created or destroyed. Some types of energy: Kinetic energy – energy associated with motion Potential energy – stored energy (many types) -spring, battery, ball at top of hill Heat energy SI unit of energy: J (joule) Work – Force exerted on an object times the distance over which it is exerted. Equation form: W=Fd SI unit of work: J (joule)

Fields Field – A physical quantity that has a value for each point in space and time. There are two types of fields in physics: 1) Vector field – both a magnitude and direction specified for each point in the field. -Field lines used to show the strength and direction in space Examples: Gravitational field, electric field, magnetic field 2) Scalar field – have only a magnitude for each point in the field. -Contour lines used to show regions where the magnitude is the same Examples: Temperature distribution in a room, pressure distribution in a fluid, voltage surrounding an electric charge

Gravitational field and force between masses: Electric field and force between charges:

Magnetic field lines: Earth’s magnetic field Bar Magnet Current carrying loop Iron filings around bar magnet

Equilibrium of mechanical systems Equilibrium - The condition of a system in which all competing influences are balanced, in a wide variety of contexts. Mechanical Equilibrium – A state in which the sum of all of the forces and the sum of all of the torques acting on a body are equal to zero. Condition 1: Sum of forces in every direction is zero Condition 2: Sum of all the torques acting on a body is zero Torque – The tendency of a force to rotate an object about an axis

Classifications of Equilibrium Points

Diffusion Diffusion – The net movement of a substance from a region of high concentration to a region of low concentration (also, movement of a substance down a concentration gradient). Gradient – Direction of greatest rate of increase. Change over a distance Examples: 1) Peeling orange, opening tuna can 2) Vacuum pump 3) Dye drop in water

Conservation Principles in Physics Conservation Principles – For isolated systems, certain quantities are held constant during its evolution. -These fundamental laws are often the starting point for solving problems in physics Examples of conserved quantities: 1) Conservation of energy 2) Conservation of linear momentum 3) Conservation of angular momentum 4) Conservation of electric charge