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science exam 2
| Question | Answer |
|---|---|
| What is a frame of reference? | it is a system of objects that are not moving with respect to one another |
| what is relative motion? | it is movement in relation to a frame of reference |
| what is distance? | it is the length of a path beween two points |
| how are distance and displacement different? | Distance is the path between two points and displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point |
| what is a vector? | it is a quantity of magnitude and direction |
| what is speed? | it is the ratio of the distance an object moves to the amount of time the object moves |
| what is instantaneous speen? | it is the rate at which an object is moving at a given moment in time |
| what is velocity? | it is a description of both speed and direction of motion. Velocity is a vector. |
| what is acceleration and how can it be positive or negative? | the rate at which velocity changes. Acceleration is a vector. If the speed goes down it negitive if it goes up its positive |
| what is changing during acceleration? | speed |
| what is instantaneous acceleration? | how fast velocity is changing |
| define force | push or pull that acts on a subject |
| what is a net force? | is the oveerall force acting on an object after all the forces are combined |
| how are balanced and unbalanced forces related to motion? | in a balanced one there is no charge in motion in an unbalanced one it accelerates. |
| explain friction | a force that opposes the motion of objects that touch as they move past each other |
| what are the four forms of friction? | static, friction, sliding, rolling, fluid |
| describe gravity | it is a force that acts between any two masses |
| what forces act on a projectile? | velocity and gravity |
| what is inertia? | is the tendency of an object to resst a change in its motion |
| list newton's three laws of motion | the state of motion of an object does not change as long as the net force acting on the object is zero. |
| explain how weight and mass are different | weight is the force of gravity acting on an object mass is the measure of inertia in an object |
| what is momentum? | it is the product of an objects mass and its velocity |
| list the four forces in nature | electromagnetic, nuclear, gravitational |
| what is pressure? | the result of distribution over an area |
| what is a fluid? | a substance or mixture that flows and has no shape of its own |
| how does water pressure change with depth? | whater pressure increases when you get deeper |
| how does air pressure change with altitude? | air pressure decreases as the altitude increases |
| what does pascal's principle mean? | a change in pressure at any point in a fluid is transmetted equally and unchangeed in all throughout the fluid |
| what are the four forces and directions acting on a body in flight? | thrust, lift, drag, weight |
| what is buoyancy? | it is the ability of a fluid to exert an upward force on an object placed on it. |
| what is the buoyant force? | the buoyant force on an obhect floats on an object is equal to the weight of the fluid displaced by the object |
| how is density related to buoyancy? | if an object is less dense than the fluid it is in it will float. if the object is more dense than the fluid it is in it will sink |
| give the definition for work | it is the product of force and distance |
| what is power | the rate of doing work |
| what is a horsepower? | it is equal to about 746 watts |
| what is the purpose of a machine? | to make owrk easier to do |
| how are inputs and outputs related to work, force, and distance? | work input = input force x input distance |
| what is meant by mechanical advavantage? | is the number of times that the machin increases an input force |
| explain the difference between actual mechanical advantage and ideal mechanical advantage | ama - equals the ratio of the output force to the input force dma - of a machine is the mechanical advantage in the absence of friction |
| what causes the difference/ | the friction is always present |
| give the formulae for calculating ama and ima | ama output/input, ima input/output |
| ist the six types of simple machines | lever, flucrum, wheel and axle, wedge, screw, pulley |
| what is a lever? | a rigid bar that is free to move around a fixed point |
| what is a fulcrum? | the fixed point the bar rotates around |
| what is an inclined plane? | is a slanted surface along which a force moves an abject to a different elevation |
| descrebe a wedge, a screw and a wheel and axle | wheel and axle - is a simple machine that consists of two disks or cylinders, screw - inclined plane wraped in a cylinder, wedge - is a v-shaped object whose sides are two inclined planes slped toward each other |
| how are fixed and movale pulleys differnet? | fixed pulley is a simple machine that consists of a rope that fits into a groove in a wheel, movable - attached to something that moves |
| what is a pulley system? | pulley systed - fixed and movable systems combined |
| how do you determine the mechanical advantage of a pulley system? | count how many pulleys are arranged |
| define energy | Energy is the ability to do work |
| what is kinetic energy? | kinitic energy is energy of motion |
| what is potential energy? | potential energy is energy that is stored as a result of position or shape |
| what are the two types of potential? | gravitational potential evergy - potential energy that depends upon an objects height , elastic potential evergy - potential energy an object that is stretched or compressed |
| list six forms of evergy and give an example of each | mechanical, thermal, chemical, electrical, electromagnetic, nuclear |
| what is energy conversion/ | energy conversion - process of changing energy from one form to another |
| explain conservation of energy | conservation of energy states that energy cannot be created or destroyed |
| what are the two components of mechanical energy? | two components of mechanical energy is motion and position |
| what is einstein's equation and what does it tell us about the universe? | energy is released as matter is destroyed |
| list the fossil fuels | oil, natural gas, and uranium are forssil fuels |
| name five renewable energy sources | hydro electric solar, geothermal, wind, biomass, and nuclear fusion - renewable energy resources |
| define heat | heat - transfer of thermal energy from 1 object to another because of the temperature difference |
| how does heat normally move? | heat flows spontaneously from hot spot to cold object |
| what is temperature? | temperature - is a measure of how hot or cold an object is compared to a reference point |
| what is thermal energy | thermal energy - the total amount of potential and kinetic energy of all paricles in an object |
| how are temperature andthermal energy different? | Temperature is a measure of how hot or cold something is. Thermal energy is the total amount of potential and kinetic energy |
| explain thermal expansion and contraction | thermal expansion occurs because particles of matter tend ot move farther apart as temperature increases |
| what is specific heat? | specific heat - is the total amount of heat needed to raise the temperature |
| what are the three ways in which hear is transfered? | conduction, convection, radiation |
| what are thermal conductors and insulators? | thermal conductors are a material that conducts thermal energy well, thermal insulators are materials that conduct thermal energy poorly |
| how does conduction occur? | when materials are touching conduction occurs |
| describe convection | convection is the transfer of thermal energy when paricles of a fluid move from one place to another |
| describe a convection current | convection current - occurs when a fluid circulates in a loop as it alternately heats up and cools down. |
| describe radiation | radiation is the transfer of energy by wavees moving through space |
| state the three laws of thermodynamics | 1st law of thermodynamics states that energy is conserved, 2nd law states that thermal energy can flow from colder objects to hotter objects only if work is done on the system, 3rd law states that absolute zero cannot be reached |
| how is an internal combustion engine different from an external combustion enginge? | external combustion engine is an engine that burns fuel outside the engine internal burns fuel inside |
| what is a mechanical wave? | material trough which a wave travels is a medium |
| what causes waves? | a disturbance in matter |
| what are the two types of waves? | mechanical, sound |
| what makes a surface wave differnet? | a surface wave is a wave that travels along a surface separating two media |
| what is the difference between the period and the frequency of a wave? | period- the time required for one cycle a complete motion that returns to its starting point |
| how would you find the wavelength of a wave? | wavelength - the length between one point on a wave and the same point on the cycle of the wave |
| if you change the wavelength of a wave, what happens to its frequency? | it changes how many complete cycles it has |
| what does the amplitude of a wave tell you? | maximum displacement of the medum from its rest position |
| what is reflection? | reflection occurs when a wave bounces off a surface that ift cannot pass through |
| what is refraction? | refraction - is the bending of a wave as it enters a new medium at an angle |
| what properties of a wave change during refraction? | one side moves slower than the other one |
| what is diffraction? | it is the dending of a wave as it moves around an obstacle or passes through a narrow opening |
| What is constructive interference? | it occurs when two or more combine to produces a wave with a larger distplacement |
| what is destructive interference? | it occurs when two or more waves combine to produce a wave with a more waves combine to produce a wave with a small er displacements |
| what is a standing wave? | it is a wave that appears to stay in one place - it does not seem to move through to a medium |
| where do you find nodes and antinodes? | node - is a point on a standing wave that has no displacement from the rest position - antinode - is a point where a crest or through midway two nodes |
| what is the speed of sound? | 342 meters per second |
| how are pitch and frequency similar? | a pitch is a frquency |
| what is ultrasound? | it is used in a variety of applications, Encluding sonar and ultrasound imaging |
| what happens to sound due to the doppler effect? | it is a change in sound frequency caused by motion of the sound source, motion of the listener, or both |
| what kinds of fields are in an electromagnetic wave? | electric and magnetic fields |
| how do those fields move in relation to each other? | electric fields and magnetic fields help form each other |
| what is the speed of light | 3.0 x 10^8 |
Created by:
menga2012
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