## Physics Vocab 2nd Semester

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frasergirl56  on February 15, 2011

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# Physics Vocab 2nd Semester

 EnergyA measure if an objects ability to do "work" (which means its ability to change or create change)
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#### Definitions

Energy A measure if an objects ability to do "work" (which means its ability to change or create change)
Joule The unit of energy defined as the energy required to push with 1 newton force or a distance of 1 meter
Potential Energy Energy due to an objects position above the ground
Kinetic Energy Energy due to an objects motion
Elastic Potential Energy Energy due to the deformation of an elastic object, such as the stretching or compressing of a spring
Internal Energy Energy due to the motion (jiggling) of molecules. An increase in this energy results in the rise in temperature or a change in phase of an object
Inelastic Collision A type of collision where kinetic energy is lost and the object often changes shape or stick together
Elastic Collision A type of collision where objects bounce off each other with no permanent change in shape and no less of kinetic energy
Law of Conservation of Momentum A law that states that for interacting objects, the total momentum before the interaction is equal to the total momentum after the interaction
Law of Conservation of Energy A law that states that energy can never be created nor destroyed, simply hanged from one form into another
Total Energy The sum of kinetic energy and potential energy
Rotational Kinetic Energy Type of kinetic energy due to the rotation of an object
Work The process of transferring energy from one object to another by applying a force over a distance
Input Force The force that you supply to a simple machine
Watt A unit of power meaning 1 Joule of work done in 1 second
Power The rate at which (or how fast) work is done
Mechanical Advantage The ratio of output force (provided by the machine) to input force (force provided by you)
Simple Machine A mechanical device that transforms input forces to output forces with no additional power supplied
Efficiency The ratio of output work to input work, often expressed as a percentage
Pseudoscience A belief or practice that is claimed to be scientific, but which does not adhere to an appropriate scientific methodology, lacks supporting evidence or plausibility, or otherwise lacks scientific status
Sliding Friction A force exerted between two surfaces sliding against each other (must be moving)
Static Friction A force exerted between two surfaces trying to slide against each other (but not yet moving)
Lubricant A fluid used to reduce friction by creating a thin layer between the microscopic "hills an valleys" of a surface
Ball Bearings Small rotating spheres that reduce friction by changing sliding motion into rolling motion
Occam's Razor Test The idea that the simpler of two possible explanations is usually the right one
Torque The measure of how much twisting force causes an object to rotate
Lever Arm The perpendicular distance from the axis of rotation to the line of action of the force. It is a factor in calculating torque.
Line of Action An imaginary line in the direction of a force and passing through the point where the force is applied
Rotational Equilibrium A condition that occurs when all the torques applied to an object add to zero (balanced torques)
Rotational Inertia A measure of how resistive an object is to rotation. it depends on the objects mass and how the mass is distributed. Its symbol is "I"
Range The horizontal distance a projectile travels before hitting the ground
Projectile Any object moving through space and affected only by gravity (usually ignore any small effect of air resistance)
Horizontal Component A part of a vector that gives the magnitude only in the horizontal direction (or x-direction)
Vertical Component The part of a vector that gives the magnitude only in the vertical direction( or y-direction)
Rotation When an object turns around an internal axis (an axis within its own body)
Revolution When an object turns around an external axis
Centripetal Force An "inward directed" force that causes an object to move in a circle (or an arc). It acts perpendicular to an objects velocity
Centrifugal Force An apparent "outward directed" force that an object seems to experience when moving in a circle (or an arc). This feeling is actually just inertia causing the body to continue in the direction it was moving
Trajectory The parabolic path that a projectile follows
Black Hole An area in space with such a strong gravitational pull that no matter or energy can escape from it. Black holes are believed to form when larger stars collapse in on themselves
Center of Mass The average location of all the mass in an object. It is represented by a point. (In most situations, it is also known as the Center of Gravity)
Gravity The weak, invisible, attractive force that exists between all objects that have mass
Weight The measure of the force of the earth's gravity pulling on an object
Law of Universal Gravitation Fg= G m^1m^2/r^2
Satellite An object that circles around another object with only gravity providing the necessary centripetal force. It follows an elliptical path called an orbit
Element A pure substance that contains only atoms with the same atomic number
Compound A substance made of 2 or more elements that cannot be separated by physical means
Proton Particle with a positive charge
Electron Particle with a negative charge
Neutron Neutral particle with zero charge
Electromagnetic Force Attraction between (+) charge on protons and (-) charge on electrons
Strong Nuclear Force Holds nucleus together
Weak Force Breaks down single neutrons by gravity
Atomic Number Number of protons in nucleus of every atom of element
Atomic Mass Number after name; Number of protons and number of neutrons
Isotope Atoms of the same element that have numbers of neutrons; They are the same element but each has a different number of neutrons
Periodic Table Chart with all the elements organized by the increase of protons in each element
Group Vertical column (similar properties)
Metals Good conductors of heat and electricity as a pure element; shiny, opaque, malleable
Nonmetals Poor conductors of heat and electricity; brittle and dull
Metalloids Weak conductors of electricity; used as semiconductors in computer circuits; both metals and nonmetals
Chemical Any substance that is composed of atoms bonded together
Ionic Bond Electrons transferred from one atoms to another
Ion Atom of molecule that has a net positive or negative electric charge
Covalent Bonds Valence electrons are shared between atoms/transferred
Chemical Equations Simplified way to show the exact number of atoms and molecules involved in a chemical reaction
Physical Change Substance changes its form but is still the same substance
Chemical Change Changes one or more substances into a different substance with different properties
Chemical Reaction System of chemical changes that involves the breaking and reforming or chemical bonds to create new substances
Activation Energy Energy needed to break chemical bonds in the reactants
Exothermic Reactions A chemical reaction in which there is a net release of energy
Endothermic Reactions When forming new bonds the product releases less energy that the original reactant
Photosynthesis Reaction of energy from sunlight stored in chemical bonds in molecules of glucose that supports energy on earth
Respiration Animals who eat plants get energy by breaking up glucose molecules
Nuclear Reaction A reaction that changes the nucleus of at least one atom; may change one element into another element; involves much more energy that chemical reaction
Chain Reaction Fission if one nucleus triggers fission of many other nuclei
Radioactive Describes atoms which are unstable and spontaneously change into other atoms by the emission of particles and/or energy from nucleus
Inference A logical conclusion based on observable facts

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