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114 Cards in this Set
- Front
- Back
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If Fast Freddy doubles his running speed, what else doubles?
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His momentum.
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A 1-kg ball has the same speed as a 10-kg ball. Compared to the 1-kg ball, the 10 kg ball has how much momentum?
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10 times as much.
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Two iron balls, one twice the mass of the other, are dropped from rest from the top of a one-story building. Compared with the lighter ball, the twice-as-heavy ball when hitting the ground below has
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twice the momentum
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If the mass of a cart full of groceries decreases to half and its speed doubles, the momentum of the cart
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remains unchanged.
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Your friend says the impulse equals momentum. You disagree and say the friend is missing an important word, which is
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Change
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The impulse-momentum relationship is a direct result of Newton's
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second law
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Which of the following equations best illustrates the usefulness of automobile air bags?
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d=1/2gt^2
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When you jump from an elevated position to the ground below, the force you experience when landing depends on
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the jumping height
and the softness or hardness of the ground and how much your knees bend (all of the above) |
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Standing on a skateboard, you toss a ball horizontally away from you. The mass of the ball is one-tenth your mass. Compared with the speed you give the ball, your ideal recoil speed will be
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one-tenth as much
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A big fish swims upon and swallow a small fish at rest. After lunch, the momentum of the big fish is
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The same as before.
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The symbol p is often used to represent
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momentum
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p =
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mv
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Different forces exerted over different time intervals can produce the same impulse:
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F(bold)t (a large change in momentum over a short time requires a large force) or t(bold)F (a large change in momentum over a long time requires a safely small average force).
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Most of a cannonball's momentum is in speed; most of the recoiling cannon's momentum is in mass. so:
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mV(bold) = m(bold)V
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When a physical quantity remains unchanged during a process, we say that quantity is
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conserved.
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Law of conservation of momentum
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In the absence of an external force, the momentum of a system remains unchanged.
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When external forces don't play a role, momentum is conserved for both ____________ and ____________ collisions.
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elastic, inelastic
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elastic collision
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a collision in which colliding objects rebound without lasting deformation or the generation of heat (like two marbles)
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Impulse
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The product of force acting on an object and the time during which it acts. In an interaction, impulses are equal and opposite.
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Impulse-momentum relationship
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Impulse is equal to the change in the momentum of the object that the impulse acts on. Ft=(triangle)mv.
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Inelastic collision
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A collision in which the colliding objects become distorted, generate heat, and possibly join together.
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Momentum
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the product of the mass of an object and its velocity.
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How much work is done on a 100-kg crate that is hoisted 2m in a time of 4s?
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work = Fd = mgd = 100(10m/s^2)(2m) = 500 J
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How much power is required to raise a 100-kg crate a vertical distance of 2 m in a time of 4 s?
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P= W/t = Fd/t = mgd/t = 2000 J/4s = 500 watts
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Raising an auto in a service station increases its potential energy. Raising it twice as high increases its potential energy by
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twice as much.
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A model airplane moves 3 times as fast as another identical model airplane. Compared to the kinetic energy of the slower airplane, the kinetic energy of the faster airplane is
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9 times as much. (3^2)
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Which of the following equations is most useful for solving a problem that asks for the distance a fast-moving box slides across a post office floor and comes to a stop?
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KE=1/2mv^2
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A shiny sports car at the top of a vertical cliff has a potential energy of 100 MJ relative to the ground below. Unfortunately a mishap occurs and it falls over the edge. When it is halfway to the ground, its kinetic energy is
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the same as its potential energy at that point.
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When a hybrid car brakes to a stop, much of its kinetic energy is transformed to
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work.
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In an ideal pulley system, a woman lifts a 100-N crate by pulling a rope downward with a force of 25 N. For every 1-meter length of rope she pulls downward, the crate rises
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25 centimeters.
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When 100 J are put into a device that puts out 40 J, the efficiency of the device is
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40 percent.
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A machine cannot multiply
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energy.
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Work =
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Force times distance.
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Power =
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Work / time
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Mechanical energy may be in the form of _______ energy of ___________ energy or ________.
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potential, kinetic, both
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No change in energy means no ________________ was done
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net work
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The amount of gravitational potential energy that an elevated object has is equal to
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the work done to lift it (force to move it times distance moved).
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Gravitational potential energy = weight times height because
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it should equal force times distance; but once upward motion begins, the force necessary to keep it going is equal to the object's weight. Also, the distance is the same as the height, of course.
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PE =
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mgh
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KE =
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1/2mv^2
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Understanding the difference between kinetic energy and momentum is
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high level physics
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Work = (other than force times distance)
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Change in energy, kinetic energy or potential
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Law of conservation of energy
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energy cannot be created or destroyed; it may be transferred or transformed, but total energy remains the same.
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work input = work output, ergo
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f x d (input) = f x d (output)
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In any machine, some energy is transformed into atomic or molecular kinetic energy, making the machine warmer. The wasted energy is
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dissipated as thermal energy, or heat
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Efficiency =
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Work done / energy used
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Except for nuclear power, the source of practically all energy is
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the sun.
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hydrogen, like electricity, is not a ________ of energy; it ________ energy.
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source, carries
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there is more energy stored in hydrocarbons than
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there is in the molecules that result when the hydrocarbon is consumed for food.
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The force of gravity between two planets depends on their
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Masses and distance apart
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When the distance between two stars is reduced by 1/2, the force between them
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increases four times as much
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If the sun were twice as massive, its pull on Mars would be
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twice as much.
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When an astronaut in orbit is weightless, he or she is
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still in the grip of Earth's gravity
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When no air resistance acts on a fast-moving baseball, its acceleration is
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downward, g.
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when you toss a projectile sideways, it curves as it falls. It will be an Earth satellite if the curve it makes
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matches the Earth's surface.
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In circular orbit, the gravitational force on a satellite is
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both constant in magnitude and at right angles to satellite motion.
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The speed of a satellite in elliptical orbit
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varies
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A satellite in elliptical orbit about Earth travels fastest when it moves
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close to Earth
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A satellite in Earth orbit is above Earth's
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atmosphere
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Newton reasoned that the Moon is falling for the same reason
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that an apple falls; due to Earth's gravity
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The ____________ of the moon allows it to fall around earth rather than directly into it
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tangential velocity
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law of universal gravitation
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According to Newton, every mass attracts every other mass with a force that is directly proportional to the product of the two interacting masses.
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Force is proportional to
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(mass1 times mass2) over distancel^2
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the inverse-square law
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the intensity of light (gravity, spraypaint) gets less as the inverse square of the distance.
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G
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the universital gravitational constant, 6.67 x10^-11
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Gravity is a very _________ force compared with electricity
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weak
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If an apple weighs 1 N on earth's surface, it weighs ___ if it were moved twice as far from the earth's center (inverse square law)
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1/4 (two squared, and then inversed)
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At 3 times the distance, the weight of a 1 N apple is
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1/9th
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The units of G make force come out in
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newtons
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When G was first measured in the 18th century, people were excited
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because newspapers announced the discovery as one that measured the mass of planet Earth.
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a projectile falls below an imaginary straight-line path
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a distance equal to the distance it would fall from rest at each point along the line
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Any satellite is simply a projectile moving fast enough to
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fall continually around planet earth
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A projectile that moves fast enough to travel a horizontal distance of
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8km/s is an Earth satellite
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Astronauts inside orbiting space facilities lack a _________; that is why they have no weight.
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Support force
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What are falling stars?
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grains of sand and other meteorites that graze the atmosphere and burn up
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The closer the foci are to each other, the closer the ellipse is to being a
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circle
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From the surface of the Earth, "escape speed" is
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11.2 km per second
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Current speculation accepts the Big Bang theory and that the event occurred
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13.7 billion years ago.
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Pumice is a volcanic rock that floats in water. The density of pumice is
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less than the density of water
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The pressure at the bottom of a pond does NOT depend on
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The surface area of a pond
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A completely submerged object always displaces its own
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volume of fluid
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A rock suspended by a weighing scale weighs 5 N out of water and 3 N when submerged in water. What is the buoyant force on the rock?
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2 N
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A block of wood with a flat rock tied to its top floats in a bucket of water. If the wood and rock are turned over so the rock is submerged beneath the wood, the water level at the side of the bucket
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remains the same
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In a vacuum, an object has no
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buoyant force
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Consider two mercury barometers, one having a cross-sectional area of 1 cm^2 and the other 2 cm^2. Mercury in the smaller tube will rise
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to the same height as the other
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In a hydraulic press operation, it is impossible for the
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energy output to exceed the energy input
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The flight of a blimp best illustrates
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archimedes' principle
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Wind speeding up as it blows over the top of a hill
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decreases atmospheric pressure there.
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Density
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a measure of how much mass occupies a given space, whether solid, liquid, or gas. Amount of matter per unit of volume. Density = m/volume
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weight density
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amount of weight per volume.
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Pressure
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pressure = force/area
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liquid pressure
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liquid pressure = weight density x depth
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Pressure in the water is due to the weight of the fluid directly above you-- both
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the weight of water plus the weight of the atmosphere
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The forces due to liquid pressure against a surface combine to produce
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a net force perpendicular to the surface. (hence water flowing out sideways and then down from a hole in a cup's wall)
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The greater pressure against the bottom of a submerged object produces
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an upward buoyant force
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If the weight of a submerged object is greater than the buoyant force, the object wiill ___________; if not, it will ___________; if equal, it will
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sink; float; remain in its level, like a fish.
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Archimedes' principle:
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An immersed body is buoyed up by a force equal to the weight of the fluid it displaces. (or gas, or whatever)
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An iron block will __________, but the same mass of iron shaped like a rectangular dish will ___________. why?
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sink; float. The greater surface area allows a greater buoyant force to act on the iron dish.
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Boyle's Law
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Pressure one times volume one = pressure two times volume two.
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atmospheric pressure is caused by
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the weight of air.
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Pascal's Principle
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a change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid. (the whole piston lifting thing)
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Any 1-cubic-meter object in air is buoyed up with a force of
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12 N
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Bernoulli's Principle
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More speed and kinetic energy mean less internal pressure, and vice versa.
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temperature-- definition, how it is measured, what effects it has on matter
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Temperature is a measure of the average heat or thermal energy of the particles in a substance. It is measured by thermometers. Kelvins, Celsius, Fahrenheit. It can change the state of matter and cause gases to expand.
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How are heat and temperature different?
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Heat is the total energy of molecular motion in a substance while temperature is a measure of the average energy of molecular motion in a substance. Heat energy depends on the speed of the particles, the number of particles (the size or mass), and the type of particles in an object. Temperature does not depend on the size or type of object. For example, the temperature of a small cup of water might be the same as the temperature of a large tub of water, but the tub of water has more heat because it has more water and thus more total thermal energy.
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Discuss absolute zero and describe the temperature scale using it.
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Absolute zero is the point where no more heat can be removed from a system, according to the absolute or thermodynamic temperature scale. This corresponds to 0 K or -273.15°C. In classical kinetic theory, there should be no movement of individual molecules at absolute zero, but experimental evidences shows this isn't the case.
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Describe specific heat capacity.
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The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.
Q=cm(triangle)T where Q=heat added, c=specific heat, m=mass, (triangle)T=change in temperature |
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Discuss thermal expansion.
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Thermal expansion is the tendency of matter to change in volume in response to a change in temperature. When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation.
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How do conduction, convection, and radiation differ? Describe each.
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Conduction is the transfer of heat between substances that are in direct contact with each other. (metal pot on a stovetop). Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas. (boiling water, atmospheric temperature changes.) Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object (the sun, heat from a lightbulb filament).
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thermal energy
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heat; Thermal energy is the part of the total potential energy and kinetic energy of an object or sample of matter that results in the system temperature. It is represented by the variable Q, and can be measured in Joules.
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unit: calorie
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approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius; equal to 4.184 J
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terrestrial radiation
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Electromagnetic radiation originating from Earth and its atmosphere
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Coulomb's Law
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Coulomb's Law is a law stating the force between two charges is proportional to the amount of charge on both charges and inversely proportional to the square of the distance between them.
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Compare electrical forces with gravitational forces
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Both forces make use of fields, and both are based on the product of the magnitudes of two scalar quantities divided by the square of their distance(they have similar equations)
The strength of both forces depends on the distance. Differences: Electric fields are both attractive and repulsive, whereas gravity is only attractive. Gravity has infinite range, electricity cannot travel too far. |
