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GHSGT Physics Review Motion One possible unit of speed is ___. a. miles per hour b. kilometers per hour c. light years per century d. all of the above e. none of the above The answer is D. Average Speed is a distance traveled divided by the time required for the trip. a. speed = distance / time b. velocity = distance / time in a direction c. An acceptable unit would be any measure of length over any unit of time. d. mi/hr, km/hr, and m/s are common units for speed or velocity. Motion Acceleration is defined as the change in ___. a. distance divided by the time interval b. velocity divided by the time interval c. time it takes to move from one speed to another speed d. time it takes to move from one place to another place e. velocity of an object The answer is B. Acceleration is the change in velocity divided by the time it took to change the velocity. a. acceleration = Δ velocity / Δ time b. Acceleration tells how fast an object is getting faster (or slower). c. Acceleration also tells if an object is changing direction. d. The units for acceleration are a distance over a time squared (i. e. m/s2). Motion Suppose you take a trip that covers 240 km in 4 hours. Your average speed is ___. a. 960 km/hr b. 480 km/hr c. 240 km/hr d. 120 km/hr e. 60 km/hr The answer is E. Speed = distance / time Speed = 240 km / 4 hr Speed = 60 km/hr Newton’s Laws A sheet of paper can be withdrawn from under a carton of milk without toppling it if the paper is pulled quickly. The reason this can be done is that ___. a. The milk carton has very little weight. b. There is an action/reaction pair operating. c. Gravity pulls very hard on the milk carton. d. The milk carton has inertia. e. none of the above The answer is D. Newton’s first law states that an object tends to retain its current state of motion unless acted on by a net force. This is the law of inertia. a. More massive objects have more inertia because they are better at resisting changes in motion. b. There was not enough friction to move the milk carton with the paper. Newton’s Laws Compared to its weight on the earth, a 10 kg object on the moon will weigh ___. a. less b. more c. the same amount The answer is A. Weight is the force that an object experiences due to gravity. An object’s weight changes depending upon where it is (i. e. on the earth, on the moon, or on Mars). a. The units for any force are Newtons. Mass is the amount of stuff in an object. An object’s mass never changes no matter where its located. a. measured in kilograms. Newton’s Laws Newton’s second law states that force is proportional to both mass and acceleration (F = m a). a. The acceleration due to gravity on the moon is less than that on earth, therefore the object will have a smaller weight. b. mass and weight are often confused. An object will have the same mass (amount of stuff) on both the earth and the moon. Newton’s Laws Newton’s third law states that, for every action, there is an equal and opposite reaction. a. Forces always act in pairs. For example, if you kick a football, your foot applies a force to the football. However, the football applies an equal and opposite force to your foot. Newton’s Laws Friction ___. a. acts in a direction that opposes the motion of an object. b. comes from microscopic bumps that act as obstructions to the object’s motion. c. is the name given to the force acting between surfaces sliding between one another. d. all of the above e. none of the above The answer is D. Friction is the force that exists between contacting objects moving past one another. a. It is caused by interactions between the objects on a microscopic scale, as in the diagram below. b. Friction on an object is always opposite the direction of the object’s motion. c. The units for friction, as for any force, are Newtons. Momentum Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour? a. the large truck b. the small truck c. Both trucks have the same momentum. The answer is A. The momentum of an object is the product of an object’s mass and velocity. a. Momentum (p) = (mass) (velocity) b. The units of momentum are kg m/s. c. Since the trucks have the same velocity, the one with the larger mass has the larger momentum. Momentum A 4 kg ball has a momentum of 12 kg m/s. What is the ball’s speed? a. 3 m/s b. 4 m/s c. 12 m/s d. 48 m/s e. none of the above The answer is A. p = (m) (v) v=p/m v = 12 kg m/s / 4 kg v = 3 m/s Work If Harry pushes an object with twice the force for twice the distance, he does ___. a. the same work b. twice the work c. four times the work d. eight times the work The answer is C. Work is the force times the distance over which the force acts. a. Work= (force) (distance) b. The units for work are Joules. b. Since there was 2 times as much force and 2 times as much distance. c. W = (2F) (2d) d. W = 4 (F) (d) e. The amount of work he did increased by a factor of 4. Power If Lydia pushes a red box that weighs 10 N for 5 m across a room in 10 seconds, and she pushes a blue box that weighs 10 N for 5 m across the same room in 5 seconds, with which box did she use more power? a. the red box b. the blue box c. She expended the same amount of power for both boxes. The answer is B Power is the work applied divided by the amount of time it took to perform the work. a. The units for power are Watts. b. Power = work / time c. Power = (10 N) (5 m) / 5 s Power = 10 Watts for the blue box (B) d. Power = (10 N) (5 m) / 10 s Power = 5 Watts for the red box Energy As a pendulum swings back and forth ___. a. Potential energy is transformed into kinetic energy. b. Kinetic energy is transformed into potential energy. c. At the lowest part of the swing, its energy is all kinetic. d. At the end points of the swing, its energy is all potential. e. all of the above The Answer is E Kinetic energy is energy of motion. Potential energy is stored energy or energy of position. a. The pendulum is at rest at the top of its swing. It has no kinetic energy, but much gravitational potential energy. b. The units for work, kinetic energy and potential energy are Joules. The answer is E. b. At the bottom of its swing, it has no potential energy because the potential energy has been converted to kinetic energy. (it is moving fast!) Simple Machines The ratio of output force to input force in a simple machine is called the ___. a. fulcrum b. pivot point c. efficiency d. mechanical advantage e. lever arm The answer is D. Mechanical advantage tells you how much a machine multiplies the force you apply. a. MA = output force / input force b. Nothing is free! The trade-off is that you apply a small force over a large distance to apply a large output force over a small distance. Think about a wrench or a ramp. c. The amount of work (force times distance) remains relatively constant with any loss due to friction. Heat Transfer Heat transfer by conduction occurs when ___. a. Electrons bump into atoms and other electrons. b. Large numbers of atoms move from place to place. c. Atoms give off heat in the form of electromagnetic waves. d. Electromagnetic waves travel from one place to another through a vacuum. e. none of the above The answer is A Conduction is the transfer of energy as particles and molecules collide with each other. To do this, the objects have to touch. conduction Heat Transfer Heat transfer by convection occurs when ___. a. Electrons bump into other electrons. b. Large numbers of atoms move from place to place. c. Atoms give off heat in the form of electromagnetic waves. d. Electromagnetic waves travel from one place to another through a vacuum. e. none of the above The answer is B. Convection is the bulk movement of heated or cooled material within a sample, as in warm air rising and cool air sinking. convection currents in boiling water Heat Transfer Heat travels from the sun to the earth by ___. a. conduction b. convection c. radiation d. insulation e. vacuumization The answer is C. Electromagnetic radiation is emitted by the sun, some of which encounters the earth, adding energy to the matter of the earth. a. Radiation is the transfer of energy by the emitting of electromagnetic radiation which is then absorbed by another object. Phase Changes Evaporation occurs when matter changes from a ___. a. gas to a solid, b. gas to a liquid c. solid to a liquid, d. solid to a gas e. liquid to a gas Condensation occurs when matter changes from a ___. a. gas to a solid, b. gas to a liquid c. solid to a liquid, d. solid to a gas e. liquid to a gas The answers are E then B. A phase change is accompanied by the absorption or the release of energy. a. A diagram for water with common phase change terms is provided below. Waves The distance between successive identical parts of a wave is called its ___. a. frequency b. period c. wavelength d. velocity e. amplitude The answer is C. Wavelength is the distance from crest to crest or trough to trough, measured in meters. Amplitude is the size of the disturbance, from center to peak or center to trough. Frequency is how many time the disturbance occurs per unit time, typically in cycles per second or Hertz. Waves Sound waves cannot travel in ___. a. air b. water c. steel d. a vacuum e. Sound can travel in all of the above. The answer is D. Sound is a mechanical wave. It requires a medium, or matter, to travel through. Electromagnetic waves do not need a medium to travel through. Electromagnetic waves from the sun travel to the earth through the nearvacuum that is outer space. Waves If the sun were to disappear right now, we wouldn’t know about it for about 8 minutes because it takes 8 minutes ___. a. for the sun to disappear b. to operate receiving equipment in the dark c. for light to travel from the sun to the earth d. all of the above e. none of the above The answer is C. Waves travel at a certain speed. Wavelength and frequency are related to speed. a. Wave speed = (frequency) (wavelength) b. Electromagnetic radiation travels at the speed of light (c) which is 3 x 108 m/s or 186,000 miles per second. The sun is so far away that it takes almost 8 minutes for these waves to reach the earth. c. Mechanical wave speed depends on the matter it is traveling in. Sound is faster in solids than liquids and slowest in gases. Light Different colors of light correspond to different light ___. a. velocities b. intensities c. polarities d. frequencies e. none of the above The answer is D. Our eyes interpret the frequency of light as color. Because frequency is related to wavelength by speed, another acceptable answer could be wavelength. However, this was not one of the choices. Light and Color Complimentary colors are two colors that ___. a. look good together b. are primary colors c. are next to each other on the color chart d. produce white light when added together e. none of the above The answer is D. Light’s primary colors are red, green, and blue. a. Red and green light make yellow light. b. Blue and red light make magenta light. c. Blue and green light make cyan light. d. Red, green, and blue light combine to make white light. Light and Color d. Hence, a primary light color and its complementary color will create white light. e. Light colors opposite each other on the wheel here produce white light. Electric Charge Two like charges ___. a. attract each other b. repel each other c. neutralize each other d. have no effect on each other e. must be neutrons The answer is B. Charges that have the same sign (negative / negative or positive / positive) will repel each other whereas charges that have opposite signs (negative / positive) will attract each other. Electricity A 10 Ω resistor has a 5 A current running through it. What is the voltage across the resistor? a. 5 V b. 10 V c. 15 V d. 20 V e. more than 20 V The answer is E. Ohm’s Law states that voltage = (current) (resistance) a. Voltage = (I) (R) b. I is the symbol for current. Current is measured in amps (A). c. R is the symbol for resistance. Resistance is measured in Ohms (Ω) d. V = (I) (R) V = (5 A) (10 Ω) V = 50 Volts Electricity To form an electric circuit, you need ___. a. a power source b. some resistance (i. e. a light bulb) c. wires or conductors to connect everything d. a complete path for the current e. all of the above The answer is E. A complete circuit needs a voltage source (like a battery), wires to connect all of the components, and a load to consume the energy (such as a light bulb or your IPOD). Electric Circuits The total resistance of a 3 Ω resistor and a 6 Ω resistor in series is ___. a. 18 Ω b. 9 Ω c. 6 Ω d. 3 Ω e. 2 Ω The answer is B. For resistors in series, add the resistances together to determine total resistance. 1 1 parallel, 1 For resistors in add the inverses of each ... R R resistor to getR the inverse of the total resistance. total 1 2 This problem involved a series circuit. Rtotal = R1 + R2 Rtotal = 3 ohms + 6 ohms Rtotal = 9 ohms series parallel Electric Circuits Equation for adding the resistors in a series circuit. Rtotal = R1 + R2 + R3 . . . . Equation for adding the resistors in a parallel circuit. 1 + 1 + 1 ..... 1 = Rtotal R1 R2 R3 End of GHSGT Physics Review