8th grade science 2nd semester exam
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| Define motion. | Distance from one object to another is changing.
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| Define reference point. | Place/object used for a comparison to determine if something is moving.
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| Give 3 exemples of reference points. | Tree, sign, building
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| Define and be able to give examples of relative motion | 1. Motion that depends on the reference point 2. cars or airplanes on a runway
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| Be able to compare relative motion from different perspective like skydivers on page 310 | Review page 310 in text book
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| What is the SI unit for distance(length) | Meters(m) or centimeters(cm)
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| What does a centi mean? | one hundredth
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| What does a milli mean? | one thousandth
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| How many centimeters are in a meter stick? | 100 cm
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| Define Speed | Distance traveled per unit of time
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| What is the difference between average speed instantaneous speed? | Average speed,
instantaneous Speed -rate in which an object is moving at a given time
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| What is Velocity? | Speed in a given direction;need to know speed and direction
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| What units are used for velocity | SI Unit;meter per second and direction
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| Define vector and give an example | Measurement that includes both magnitude and direction example: Velocity
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| What does slope represent | How fast one variable in relation to the other variable or rate of change
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| How do you calculate slope? | slope = rise/run
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| If the slope of a straight line is constant the the speed of the object is | fast, steady, speed
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| If the slope of a straight line is zero then the speed of the object is | stationary
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| If the slope of a straight line curved, then the speed of the object is | getting faster
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| define acceleration | rate at which velocity changes
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| List 3 ways to accelerate | 1. Increase speed 2. decrease speed 3. changing direction
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| What is deceleration? | An object as it begins to slow down, negative acceleration
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| What are the units for acceleration(of an object moving in a straight line) ? | SI Units=meters per second per second or m/s^2
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| Be able to explain acceleration . For example what does 8 m/s^2 mean?(see page 322 for text and diagram. ) | Objects speed increases by 8 m/s every second
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| Explain the difference between zero speed and zero acceleration | zero speed - there is no motion
zero acceleration - there is no change in velocity
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| Define Force | push or pull
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| What is SI unit for force | Newton (N)
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| Is Force a vector ? | Yes
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| What is net force? | Combination of all forces acting on an object
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| How can you find the net force of two forces acting in the same direction? in opposite direction? | 1.Sum of the two individual forces 2. Difference between two individual forces
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| Can you distinguish between balanced and unbalanced forces? | Balanced-equal forces acting on one object in the opposite direction Unbalanced - causes a change in objects motion
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| UnBalanced forces can cause an object to do what 3 things? | 1. Start moving 2. stop moving 3. Change direction
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| Unbalanced forces on an object always result in what ? | change an objects movement
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| Do balanced forces acting on an object change the objects movement? | No, equal forces are exerted the net force is zero
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| friction is a force caused by what? | Forces that two surfaces exert on each other
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| The strength of friction depends on what two things? | 1. how hard the surfaces push together and 2. types of surfaces involved
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| friction always acts in what direction? | a direction opposite to the direction of the objects motion.
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| list four kinds of friction and give examples of each. | 1 static-sliding a desk 2 sliding- cars brakes 3 rolling- skateboard
4fluid-surfer
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| what factors affect the friction between two surfaces? | 1 how hard they are pushing against each other
2 what type of surface (how smooth)
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| define gravity | force that pulls objects towards each other
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| what are factors affect gravitational attractions | 1 mass 2 distance
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| define law of universal gravitational. | force of gravity acts between all objects in the universe
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| what is mass and what is weight? be able to distinguish between them. | mass-amount of matter in an object
weight-measure of gravitational force exerted on an object ex scales
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| what are the units for mass and the units for weight? why aren't they the same? | mass -kilogram mass is not effected by gravitational force
weight -pounds
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| be able to explain why your weight on the moon and your weight on the earth are different. | wight less on moon because moon's mass is only a fraction of the earth's
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| according to our scientific definition, what is free fall? | when the only force acting on an object is gravity
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| when are object on earth in free fall? | when an object falls
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| define acceleration due to gravity on earth. | the further an object falls its velocity increases
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| what is the value for acceleration due to the gravity on earth | 9.8 meters per second sqaured
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| How is acceleration due to gravity abbreviated | g
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| what terminal velocity? Can a sky diver have terminal velocity | Force of air resistance equals the weight of an object, yes
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| state Newtons first law of motion | an object at rest will remain at rest and an object moving at constant velocity will remain at a constant velocity unless acted upon by unbalanced force.
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| what are two unbalanced forces on earth that are always unbalanced | gravity and friction
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| what is inertia on what property does inertia depend | tendency of an object to resist a change in momentum. mass
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| why is the first law of motion sometimes called the law of inertia | to stop inertia an unbalanced force must be applied
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| state Newton's 2nd law of motion | acceleration depend on the object mass and on net force acting on the object.
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| what if the formula for force | acceleration equals net force over mass
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| what other units comprise a newton | kg(m/s2)
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| state newtons third law | for every action there is an equal but opposite reaction
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| when given a scenario be able to identify an action force and reaction force | ex. hitting a volleyball
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| Define momentum | quantity of motion of a moving body measured by calculting the bodies mass and velocity
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| What are units for momentum | kilograms and meters per second
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| What does the law of conservation of momentum state? | in the absence of outside forces, the total momentum of objects that interact does not change.
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| Since momentum is conserved, it is never lost but can be | transferred
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| Explain how rockets lift off using Newton's 3rd law. what is the action force? what is the reaction force? | exhaust gases push downward at high velocity rocket's exhaust gases push downwards rocket rises and gases push upwards on rocket.
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| define satellite | object that orbits another object in space
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| what is the SI unit for pressure? | pascal
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| what is a fluid and what causes fluid pressure? | fluid:material that can easily flow;caused by individual partials in a fluid.
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| what is atmospheric pressure and what causes it? | weight of the air pushing down; caused by gravity
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| what happens to atmospheric pressure as elevation increases? as elevation decreases? | decreases increases
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| what is water pressure and what causes it? | water pushing down on you; gravity
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| what happens to water pressure as depth increase? as depth decreases | increases decreases
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| what is buoyant force? | upward force
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| what is buoyancy? | ability to float it acts in the direction opposite to gravity
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| what does archimedes principle state? | buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces
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| use archimedes principle to explain how a ship floats. | it displaces the same amour of fluid equal to the weight of the object
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| Define Density | mass per unit of volume
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| what does paschals principal state | when force is applied to a confined fluid the change in pressure is transferred eqully parts of the fluid
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| what are some examples of paschal's prinicples in everyday life | brakes, barber chair, hydolic life
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| how does a hydraulic system work | multiplies force by applying force to a small area
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| what are some examples of thing that use hydraulics | dump truck, backhoes, screw plows
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| what is the definition of work | exert force on an object causing the object to move
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| what are the units for work | joules
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| what two things does work depend on | force and distance
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| energy makes work easier by | changing the amount of energy, distance and direction
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| the force you apply to the machine is the | input force
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| the force the machine applies to the object | output force
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| the force that you apply over the distance is | input work
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| the force the machine applies over distance | output work
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| in real life output work is | less than input work
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| define energy | ability to work or cause change
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| what the si units for energy | joules
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| KE kinetic energy depends on what two things | mass and velocity
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| which has a greater effect mass or velocity | velocity because its squared doubling velocity will quadruple its kenitic energy
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| PE potential energy) is due to an objects | position and shape
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| gpe (gravitational potential energy) | weight and height
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| GPE depends on two things | an objects weight and height
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| what is the elasticity of PE giving and example | potential associates with objects that can be stressed or compressed, bow strings
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| what does it mean for energy to be transformed | when one energy form is transformed into another energy form.
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| give some examples of energy transformation | toaster oven>eletrical energy to thermal energy
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| strike a match > mechanical to thermal to electro magnetic energy |
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| what is the law of conservation of energy | when one form of energy is transferred to another form of energy
no energy is destroyed in the process
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| what does Einstein have to do with law of conservation of energy | he discovered that matter can be transferred to energy therefore in some situations energy is not conserved
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| waves | disturbance that transfers energy from place to place
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| medium | material through which a wave travels
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| chemical wave | waves that require a medium from which to travel
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| vibrations | repeated back and forth or up or down motion
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| transverse wave | waves that wave that move through medium at right angles
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| longitudinal waves | waves that move medium parallel to the way it travels
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| standing wave | wave appear not to move really two waves are pushing through each other
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| wave length | this is between to cooresponding parts of a waves
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| amplitude | max distance the medium carries away the wave from the rest position
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| frequency | number of complete waves past a point in a certain amount of time
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| crest | high part of transfer waves
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| trough | low part of a transfer wave
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| compression | in longitudinal wave they are part of the medium are close together
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| refraction | part of the medium that are spread out
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| node | points of zero amplitude on a standing wave
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| how do you find the amplitude of a transverse wave | measure the distance from the rest to crest of the wave.
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| how do you find the amplitude of a longitude wave | measure how compressed or refracted the medium becomes
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| refraction occurs when a wave strikes a surface and cannot pass through |
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