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Chapter 5: Motion, Forces, Simple Machines
vocabulary
18
Science
7th Grade
12/13/2012

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Term
average speed
Definition

the distance traveled over a period of time

s=d/t

Term
instantaneous speed
Definition

the speed of an object at any instant of time,

the speed given by the speedometer

Term
velocity
Definition
the speed of an object and its direction of motion
Term
acceleration
Definition

change in velocity divided by the time needed for the change to happen,

a=final velocity - begin velocity


time

Term
force
Definition
a push or pull
Term
Newton's laws of motion
Definition
a set of principles that explain the motion of objects
Term
Newton's First Law
Definition
an object will not change its motion unless an unbalanced force acts on it
Term
friction
Definition
a force between two surfaces in contact that resists motion, always acts opposite to the direction of the motion
Term
inertia
Definition
the tendency to resist a change in motion
Term
Newton's Second Law
Definition

a change in motion occurs only if a net force is exerted on an object.

a=F/m

Term
Newton's Third Law
Definition

when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.

action-reaction

Term
work
Definition

happens when a force causes an object to move in the same direction as the force that is applied

W=Fd

Term
simple machine
Definition

uses only one movement:

screwdriver, pulley, lever, wheel and axle, inclined plane, wedge and screw

Term
compound machine
Definition
combination of simple machines:  can opener combines lever and wedge
Term
mechanical advantage (MA)
Definition

The amount machines make it easier to do a job:

MA=force out/force in

Term
pulley
Definition
has a groove with a rope or cable running through it, changes direction of a force
Term
lever
Definition
a rod or plank that pivors about a fixed point called a fulcrum
Term
inclined plane
Definition
a sloped surface, a ramp
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