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65 Cards in this Set

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