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35 Cards in this Set
- Front
- Back
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How is work calculated?
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Work is calculated by multiplying the force by the distance over which the force is applied
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work equation
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work = force x distance
W = Fd F= kgm/s2 (N) d= m W= kgm2/s2 (J) |
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when is work zero?
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when an object is not moving
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What is the relationship between work and power?
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Power is the rate at which work is done, or how much work is done in a given amount of time.
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power equation
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P=work/ time
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what is power measured in?
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watts
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How do machines make work easier?
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Machines help do work by changing the size of an input force, the direction of the force, or both.
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mechanical advantage equation
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m.e.= out F/ in F
m.e.= in d/ out d |
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What are the six types of simple machines?
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levers, pulleys, wheel and axle
ramp (inclined plane), wedge, screw |
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levers
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levers, pulleys, wheel and axle
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inclined planes
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ramp, wedge, screw
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What are the two principal parts of all levers?
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All levers have a rigid arm that turns around a point called the fulcrum.
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how many classes are levers divided into?
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3
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what are pulleys?
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modified levers
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what is the point in a pulley like?
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the fulcrum of a lever
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what does the rest of the pulley behave like?
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the rigid arm of a first-class
lever |
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examples of wheel and axles
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steering wheel, screwdrivers, cranks
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How does using an inclined plane change the force required to do
work? |
Pushing an object up an inclined plane requires less input force than lifting the same object does.
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what is a wedge?
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a modified inclined plane
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what is a screw?
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an inclined plane wrapped around a cylinder
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examples of screws
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drill bit, jar lid
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What simple machines make up a pair of scissors?
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A pair of scissors uses two first-class levers joined at a common
fulcrum; each lever arm has a wedge that cuts into the paper. |
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What is the relationship between energy and work?
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Whenever work is done, energy is transformed or is transferred from
one system to another system |
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energy is measured in what?
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joules
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Why is potential energy called energy of position?
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because it results from the relative positions of objects in a system
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what does gravitational p.e. depend on?
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mass and height
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potential energy equation
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PE= mgh
m= mass (kg) g= gravity (9.8 m/s2) h= height (m) (kgm2/s2) |
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What factors does kinetic energy depend on?
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the mass and the speed of an object
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kinetic energy equation
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KE= (1/2) mv2
m= mass (kg) v= velocity (m/s) (kgm2/s2= J) |
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what does kinetic energy depend on more than mass?
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speed
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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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How do living things get energy from the sun
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photosynthesis
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Where does the sun get energy from?
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nuclear reactions; fission and fusion
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3 fields energy can be stored in
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electric, gravity, magnetic
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how does light carry energy across empty space?
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by electromagnetic waves
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