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# Phys 11

### Physical Science 2009

Question | Answer |
---|---|

inertia | the property by which objects resist changes in motion friction, force that stops objects in motion in a vacuum the object has no air resistance so it will move forever |

mass | the quantity of matter in an object. more specifically, it is the measure of the inertia of sluggishness that an object exhibits in response to any effort made to start, stop, or deflect it, or change in any way its state of motion. |

weight | the force due to gravity on an object or the gravitational force with which a body presses against a supporting surface. |

kilogram | unit of mass. one kilogram (kg) is the mass of one liter of water at 4'c |

Force | a push or pull |

Newton | the scientific unit of force |

volume | quantity of space an object occupies |

net force | the combo of all forces that act on an object |

vector quantity | a quantity whose description requires both magnitude and direction |

vector | an arrow to represent the magnitude and direction of a quantity |

equilibrium rule | the vector sum of forces acting on a non-accelerating object equals zero: E F=0 |

support force | the force that supports an object against gravity, often called the "normal force" |

friction | the resistive force that opposes the motion or attempted motion of an object past another with which it is in contact, or through a fluid. slows obj down b/c it adds in opposite direction to oppose motion. |

air resistance | the force of friction acting on an object due to its motion in air |

speed | the distance traveled per time |

velocity | the speed of an object and specification of its direction of motion |

acceleration | the rate at which velocity changes with time; the change in velocity may be in magnitude or direction or both, usually measured in units of m/s2 |

free fall | falling only under the influence of gravity-falling without air resistance |

hang time | the time that one's feet are off the ground during a vertical jump |

scientific method | A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses |

Galileo | responsible for scientific method, coined term "inertia" and improved the telescope |

normal force | surface that objects rest on (like a table) always perpendicular to the surface (provides support for object) |

speed | V=distance/time [m/s] |

displacement | difference between final and initial position triangle = change (final - initial)change in position of object measured in meters ex. if you end where you begin the displacement is zero. |

distance | (meter) is not the same as displacement |

reference frame | shows zero point |

Newton's first law of motion | every object continues in a state of rest, or in a state of motion in a straight line at constant speed, unless acted upon by a net force. |

Newton's second law of motion | the acceleration produced by a net force on an object is directly proportional to the net force, in in the same direction as the net force, and is inversely proportional to the mass of the object. |

free fall | falling only under the influence of gravity--falling without air resistance. |

terminal speed | the speed at which the acceleration of a falling object terminates when air resistance balances its weight. |

terminal velocity | terminal speed when direction is specified or implied. |

interaction | mutual action between objects during which each object exerts an equal and opposite force on the other. |

force pair | the action and reaction pair of forces that occur in an interaction. |

Newton's third law of motion | whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. |

momentum | the product of the mass of an object and its velocity. |

impulse | the product of the force acting on an object and the time during which it acts. |

law of conservation of momentum | in the absence of an external force, the momentum of a system remains unchanged. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event. mv(before event)=mv(after event) |

elastic collision | a collision in which colliding objects rebound without lasting deformation or the generation of heat. |

inelastic collision | a collision in which the colliding objects become distorted, generate heat, and possibly stick together. |

energy | the property of a system that enables it to do work. |

work | the product of the force and the distance moved by the force W= Fd More generally, work is the component of force in the direction of motion times the distance moved. |

potential energy | the energy that matter possesses because of its position. gravitational PE=mgh |

kinetic energy | energy of motion, quantified by the relationship Kinetic energy=1/2mvsquared |

Work-energy theorem | the work done on an object equals the change in kinetic energy of the object. Work=changeKE work can also transfer other forms of energy to a system. work can also transfer |

law of conservation of energy | energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. |

power | the rate of doing work: power=work/time more generally, power is the rate at which energy is expended. |

machine | a device such as a lever or pulley that increases (or decreases) a force or simply changes the direction of a force. |

lever | a simple machine consisting of a rigid rod pivoted at the fixed point called the fulcrum. |

conservation of energy for machines | the work output of any machine cannot exceed the work input. in an ideal machine, where no energy is transformed into thermal energy, workinput=workoutput, (Fd)input=(Fd)output |

efficiency | the percentage of the work put into a machine that is converted into useful work output. (more generally, useful energy output divided by total energy input.) efficiency=useful energy output/total energy input |

law of universal gravitation | every body in the universe attracts every other body with a force that, for two bodies, is directly proportional to the product of their masses and inversely proportional to the square of the distance separating them: F=G m1m2/dsquared |

inverse-square law 1 | the intensity of an effect from a localized source spreads uniformly throughout the surrounding space and weakens with the inverse square of the distance Intensity=1/distancesquared |

inverse-square law 2 | gravity follows an inverse-square law, as do the effects of electric, light, sound, and radiation phenomena. |

weight | the force that an object exerts on a supporting surface (or, if suspended, on a supporting string), which is often, but not always, due to the force of gravity. |

weightless | being without a support force, as in free fall. |

projectile | any object that moves through the air or through space under the influence of constant gravity only. |

parabola | the curved path followed by a projectile under the influence of constant gravity only. |

satellite | a projectile or small celestial body that orbits a larger celestial body. |

ellipse | the oval path folowed by a satelite. the sum of the distances frm any point on the path to 2 points called foci is a constant. When the foci r together at one point, the ellipse is a circle. As the foci get farther apart the ellipse becomes more eccentric |

escape speed | the speed that a projectile, space probe, or similar object must reach to escape the gravitational influence of Earth or of another celestial body to which it is attracted. |

density | the amount of matter per unit volume. density=mass/volume weight density is expressed as weight per unit volume. |

pressure | the ratio of force to the area over which that force is distributed: pressure=force/area liquid pressure=weightdensityxdepth |

buoyant force | the net upward force that a fluid exerts on an immersed object |

Archimedes' principle | an immersed body is buoyed up by a force equal to the weight of the fluid it displaces (for both liquids and gases). |

principle of flotation | a floating object displaces a weight of fluid equal to its own weight. |

Boyle's law | the product of pressure and volume is a constant fro a given mass of confined gas regardless of changes in either pressure of volume individually, so long temperature remains unchanged: P1V1=P2V2 |

atmospheric pressure | the pressure exerted against bodies immersed in the atmosphere resulting from the weight of air pressing down from above. At sea level, atmospheric pressure is about 101 kPa. |

barometer | any device that measures atmospheric pressure |

Pascal's principle | a change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid. |

Bernoulli's principle | the pressure in a fluid moving steadily without friction or outside energy input decreases when the fluid velocity increases. |

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