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Machines and Force
Unit test on Forces,Work, Energy and Machines
45
Science
8th Grade
02/03/2013

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Term
Force
Definition
a push or pull that acts on an object
Term
3 types of forces
Definition
Contract, Friction and Action at a Distance
Term
Contract Force
Definition
must touch an object to push or pull, such as a racket hitting a ball
Term
Friction force
Definition
a force that is opposite to the motion of an object, such as a puck sliding on the floor
Term
Action at a Distance force
Definition
can push or pull without touching an object such as gravity, magnetism or static electricity
Term
Mass
Definition
the number of particles in an object, the amount of matter
Term
Weight
Definition
the amount of force an object has due to gravity pulling it downward
Term
Difference between mass and weight
Definition
Mass does not change with gravity. Weight does change with gravity. You weigh less on the moon but have the same mass.
Term
Newton
Definition
a unit of Force
Term
A Unit of Mass
Definition
kilograms or grams
Term
Measure of Acceleration
Definition
m/s2, the measure of gravity
Term
Equation to calculate force
Definition
Force = Mass X Acceleration or F = M x A
Term
Two ways to calculate force
Definition
use F=MxA equation or using a Newton Scale
Term
Work
Definition
when force causes an object to move a distance
Term
Energy
Definition
the ability to work
Term
Joule
Definition
unit to measure both work and energy
Term
2 types of energy
Definition
Kinetic and Potential
Term
Kinetic
Definition
the energy of an object in motion
Term
Potential
Definition
Energy that is stored to use later
Term
5 types of Kinetic energy
Definition
light, sound, heat, electrical and mechanical
Term
3 types of Potential energy
Definition
chemical, elastic, gravitational
Term
Light energy
Definition
kinetic - energy that allows us to see, ie a light bulb
Term
Sound energy
Definition
kinetic - energy caused by moving waves, ie blowing a whistle
Term
Heat energy
Definition
kinetic - energy caused by moving particles or friction, ie rubbing your hands together
Term
Electrical energy
Definition
kinetic - energy caused by flowing electricity or electrons, ie lightning
Term
Mechanical energy
Definition
kinetic - energy that does work, ie turning gears
Term
Chemical energy
Definition
potential - eneregy caused by a chemical reaction, ie eating food
Term
Elastic energy
Definition
potential - energy caused by a stretched object, ie a spring
Term
Gravitational energy
Definition
potential - energy caused by gravity, ie a dropping glass
Term
Law of Conservation of Energy
Definition
energy cannot be created or destroyed, it can only be changed from one form to another, so the amount of energy into a system equals the amount of energy that comes out
Term
Calculating Work
Definition
work = Force X Distance or W = F x D
note work will be in J or Nm units
Term
Machine
Definition
device made up of fixed and moving parts that do a specific job, or a device that reduces the force required to do a job
Term
3 ways machines help
Definition
increase the force applied, increase the distance over which the force is applied or change the direction of a force
Term
Machine that increases force applied
Definition
a nutcracker
Term
Machine that increases the distance over which force is applied
Definition
a ramp between two heights, like on the back of a moving truck
Term
Machine that changes the direction of the force applied
Definition
a pulley on a flag pole or a teeter totter
Term
Two types of force with a machine
Definition
input force and output force
Term
Input Force
Definition
the force applied to the machine
Term
Output Force
Definition
the force the machine applies to the object
Term
Mechanical Advantage
Definition
the amount by which a machine multiplies an input force, how much greater the output is because of the machine.. it is the amount of work a machine adds
Term
Units to measure mechanical advantage
Definition
there are no units, it is a multiple of .. ie the machine increased the force by 5 times
Term
Mechanical Advantage formula
Definition
MA = Output Force / Input force
Term
Ideal Mechanical Advantage
Definition
when a distance value is used to calculate mechanical advantage
IMA = input distance / output distance
Term
First Class Lever
Definition
requires more output force, but the input force will move a greater distance. example a hammer removing a nail
Term
Third Class Lever
Definition
Requires more input force, input will move shorter distance and output will have greater speed. ie a hockey stick being used to shoot a hockey puck, the hand moves a little, the stick or lever moves more and puck moves fast
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