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65 Cards in this Set
- Front
- Back
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What is work?
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Occurs when a force is applied over a distance & the object moves in the direction of the applied force
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1J equals?
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1 n*m 1kgm2/s2
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What happens when an object doesn't move?
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There is no work
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What is power?
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The rate at which work is done
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1 watt equals?
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1 J/ s
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The more quickly work is done...
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the more power you have
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What is asimple machine?
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the most basic machines that are the bases for all other machines
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What are the 6 types of simple machines?
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Lever, pulley, wheel and axle, the inclinded plane, wedge, screw
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What are the two types of families?
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Lever, and the inclinded plane family
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How many classes do levers have?
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3
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What is the first class lever?
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fulcrum is in the middle and input and output forces are on opposite ends
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Ex: of a first class lever
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see saw, claw hammer, crow bar
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ex: of a second class lever:
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wheel barrow, hinged door, nutcracker
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What is a second class lever?
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Fulcrum is at one end, the input distance is at the other end, and the output force is in the middle.
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Second class lever does what?
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Always multiplies force
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What is a third class lever?
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Fulcrum is at one end, the input force is in the middle, and the output force is at the opposite end
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What is an example of a third class lever?
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baseball bat, broom
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The lever family?
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All levers have a rigid arm that turns over the point called a fulcrum
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Tell me about the input force of a lever?
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The input force ( the force someone applies) is multiplied or redirected into an output force ( the force exerted by the machine)
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What is a pulley?
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the point in the middle of the pulley is the fulcrum and the rest of the pulley is the arm
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What is the MA of 1 pulley?
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One pulley doesnt have an advantage other than changing the direction of the force
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What multiplies pulleys?
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Block and tackle
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What makes work easier. (dealing with pulleys)
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work is easier with more than one pulley
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What is a wheel and axle?
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made of a wheel ( the lever or pulley) and an axle (shaft)(fulcrum)
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What happens with a wheel and axle(pertaining to the force)
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a small input force is applied and is multiplied into a larger output force
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Examples of a wheel and axle?
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steering wheel, screwdriver, crank
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What is the inclinded plane family?
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pushing an object up an inclined plane required less input force than lifting the same distance against gravity
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What do you do in an inclined plane?
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you apply less force in the direction parellel to the ramp over longer distance
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What is a wedge?
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2 inclinded planes back to back
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What does a wedge do?
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one force directed down turns into two forces directed to the sides
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Examples of a wedge?
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chopping wood
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What is a screw?
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an inclinded plane wrapped around a cylinder
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Examples of an inclinded plane?
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screw, drill bit, spiral staircase
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What is a compound machine?
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a machine that combines 2 or more simple machines
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examples of compound machines?
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car, bycicle, scissors--->2 first class levers, car jack---> wheel & axle, levers
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What does mechanical advantage do?
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machines help do work by changing the size of the input force, the direction of the force or both
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What is mechanical advantage?
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the ratio between the output force and the input force. it is alse equal to the ratio between the input distance and the output distance if friction is ignored
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MA>1
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-----> force is multiplied
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MA<1
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----> distance is increased
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What is energy?
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the ability to do work?
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What happens when work is done?
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energy is transferred from one system to another or it is transformed
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What is potential energy?
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energy that results from the relative positions of objects in a system
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What is elastic potential energy?
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Potential energy resulting from an object being stretched or compressed to increase or decrease the distance between parts
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examples of elastic potential energy?
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spring, rubber band
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What is gravitational potential energy?
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potential energy that results from 2 or more objects being seperated by a vertical distance and there is gravitational attraction between the objects
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SIDE NOTE!
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WATCH HEIGHT IT CAN BE FROM THE GROUND OR RELATIVE
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What is kinetic energy?
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the energy that an object has because it is moving
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what does kinetic enrgy depend on?
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depends on both mass and velocity but velocity impacts it more because it is squared
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what is mechanical energy?
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the sum of the kenetic energy and the potential energy of the system
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What is nonmechanical energy?
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energy that lies at the level of the atom
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What are many types of mechanical energy?
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potential and kenetic energy
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What is chemical energy?
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energy stored in chemical bonds that relates to the relative positions of atoms in a substance
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what is photosynthesis?
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a chemical process that takes energy from the sun and converts it into chemical energy
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what is nuclear energy?
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energy stored by the forces that hold subatomic particles together in the nucleus of an atom
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what is eletric energy?
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energy that results from the location of charged particles in an aletric field
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NOTE:
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AS ELECTRONS MOVE IN AN ELETRIC FIELD A MAGNETIC FIELD IS CREATED
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What is light energy?
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light that carries energy in the form of lectromagnetic waves
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What is energy transformations?
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energy changes from one state to another but the total amount remains the same
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Mechanical energy to nomechanical energy?
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heat, light due to friction or air resistance
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1st law of thermodynamics
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for any system the net change in energy equals the energy transferred as work and as heat
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Open system?
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system in which energy and matter are exchanged with the surroundings
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closed system?
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system in which energy is exchanged with the surroundings but not with matter
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isolated system?
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system in which neither energy nor matter are exchanged with the surroundings * BEST
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Efficiency?
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a measure of how much useful work a machine can do
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100% effiency=
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perpetual motion machine
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