Motion The base SI units for length, time, and mass are meters, seconds, and kilograms Movement in relation to a frame of reference is called relative velocity Vectors (like velocity) have both magnitude and direction; scalars (like speed) only have magnitude The slope of a Distance versus Time graph tells us the average speed Velocity is calculated by dividing displacement by time

Motion Acceleration is the rate at which velocity changes Objects that are accelerating have parabolic Distance versus Time graphs Adding vectors together results in another vector Changing direction or speed will be the result of acceleration

Forces Mass is a measurement of inertia Static friction is the friction when an object hasn’t started to move yet If the net force is zero, an object’s velocity will not change F = ma p = mv

Forces Momentum is conserved if there are no net forces acting on a system Impulse is the change in momentum, and is the product of force and time The electromagnetic force is the only one that can both attract and repel The strong nuclear force holds together protons and neutrons The gravitational force is the weakest of the fundamental forces, but is the most easily observed when dealing with large objects

Forces Newton’s Law of Universal Gravitation states that all mass is attracted to all other mass Action-reaction forces do not cancel out because they act on different objects Forces can be acting on objects that are either moving or not moving Forces do work when they are applied in the direction of motion

Work & Energy Power is the rate of doing work Machines output less work than is put into them because friction makes their efficiency less than 100% Actual Mechanical Advantage < Ideal Mechanical Advantage Machines change the size of force, the direction of force, and/or the distance of force

Work & Energy Work transfers energy Mechanical energy is potential + kinetic Energy is conserved Friction turns kinetic energy into thermal energy E = mc 2 Fossil fuels (coal, oil, natural gas) represent the majority of energy resources in use Energy gets changed from one form to another

Waves Waves transfer energy Transverse waves are perpendicular & longitudinal waves are parallel to propagation; surface waves are both v = fλ Diffraction is when a wave bends around an obstacle; the longer the wavelength, the more it bends Wave amplitude determines energy The Doppler Effect explains why there is an apparent change in frequency when there is relative motion between a wave source and an observer

Waves Refraction involves the change in direction of a wave because of a change in speed Electromagnetic waves can travel through empty space (a vacuum) Mechanical waves require a medium in which to travel Waves can interfere, matter cannot

Light Polarized waves only oscillate in one direction Radio waves have low frequency and long wavelength, low energy and penetrate less Gamma rays have high frequency and short wavelength, more energy and penetrate more The Photoelectric Effect is when electrons are emitted from a metal when high frequency light hits it

Light Mirages are caused by total internal reflection Light is both a particle and a wave Thomas Young’s double-slit experiment showed light interfering and acting wavelike All electromagnetic waves have the same speed for a given medium

Electricity Electric charge can be positive or negative The SI unit for charge is Coulombs Opposite charges attract, likes repel Electric force depends directly on the size of the charges and inversely with the square of the distance Charge is conserved Objects can be charged by friction, induction, and conduction

Electricity Resistance depends directly on temperature and length, and inversely with width V = IR Current is measured in Amps In parallel circuits, each element functions independently P = IV Grounding, fuses, and circuit breakers are common electrical safety devices

Electricity In series circuits, either everything works or nothing works Metals and other conductors have electrons that are free to move; plastic and other insulators do not Electric fields lines point away from positive charges and towards negative charges The electric force is responsible for contact forces like friction and the normal force

Magnets Magnetic fields are strongest near the poles Magnets always have both a north and a south pole Magnetic materials are magnetized when their magnetic domains are aligned Magnetism is ultimately caused by moving charges A solenoid is a stack of loops of wire Faraday’s Law relates changing magnetic flux to induced currents

Magnetism Motors convert potential energy (chemical, electric, etc.) into mechanical energy Moving charges are deflected perpendicular to magnetic fields and their velocities Transformers change AC voltages via inductance The earth’s magnetic field is caused by convection currents in its mantle The strength of an electromagnet is directly proportional to the number of coils and current