Spring Final Science--Physics

work

energy transferred to a system by an external force when it acts on the system to move it

power

the rate of doing work

simple machines

a basic mechanical device that changes the magnitude, direction, or distance traveled of the force used when doing work

mechanical advantage (MA)

the amount which a simple machine multiplies an input force to produce an output force

actual mechanical advantage

the mechanical advantage that accounts for all mechanical losses sustained through using a machine i

ideal mechanical advantage

the mechanical advantage for an ideal machine (100% efficient) with no friction

lever

a simple machine that consists of a rigid bar that turns about a pivot point (the fulcrum)

fulcrum

the point about which a lever pivots or rotates

rotational motion

the motion of an object around some axis

torque

a force that tends to cause a rotation around a pivot point (measured in Joules)

first class lever

a lever in which the fulcrum is between the input and output forces

second class lever

a lever in which the output force is between the input force and the fulcrum

third class lever

a lever in which the input force is between the output force and the fulcrum

wheel and axle

a simple machine consisting of a wheel with a rod running through its axis that acts as the pivot point

gear

a simple machine that consists of a wheel with teeth on its perimeter that mesh with similar teeth of other gears to do work

pulley

a simple machine that consists of a wheel and axle system with a groove around the perimeter of the wheel in which a rope, cable, or belt moves with the wheel as it rotates

inclined plane

a simple machine that consists of a plane whose opposite ends are at different heights

wedge

a simple machine consisting of two inclined planes attached at an acute angle and used to spread a material apart as it is forced into the material

screw

a simple machine that consists of an inclined plane wrapped around a cone or cylinder in a spiral pattern

compound machine

a machine that combines two or more simple machines

law of torques

the law that states that in a lever system in rotational equilibrium, the sum of the torques must be zero

mechanical advantage greater than 1

force multiplier, apply less force over greater distance

mechanical advantage less than one

force reducer, apply more force to get greater distance

mechanical advantage = 1

changes direction of force

moment arm

distance from the rotational axis to the location where the force is applied

single fixed pulleys

rope goes over pulley and attaches to the load, redirects force

rope segments

number of rope setting holding up the load is the ideal mechanical advantage of a pulley system

pulley mechanical advantage

greater than or equal to one

block and tackle

a system of fixed and movable pulleys connected by ropes

more ropes

=less efficient

inclined plane mechanical advantage

always greater than 1

steepness of an inclined plane

steeper, close mechanical advantage is to one

mechanical advantage of compound machines

sum of simple machine mechanical advantages

force (F)

a push or pull on an object

dynamics

the branch of physics that studies forces and how they change an object’s motion

contact force

a force that acts only when one object touches another

field force

a force that acts between objects that are not touching, also called a force at distance

free body diagram

a sketch that shows an object and the forces acting on it; also called a force diagram

balanced forces

simultaneous forces whose pushes and pulls cancel each other out

unbalanced forces

a collection of forces on an object that don’t cancel our and thus cause an acceleration

inertia

the tendency of matter to resist changes in its motion

Why was Galileo unable to formulate equations to desrcibe motion?

lack of technology

Newton’s First Law of Motion (Law of Inertia)

Objects at rest remain at rest, and objects in motion continue in a straight line at a constant velocity (speed and direction) unless acted on by a net force

Newton’s Second Law of Motion—law of acceleration

the acceleration of an object is directly proportional to the net force acting upon the object and is inversely proportional to its mass

Newton’s Third Law of Motion—law of action-reaction

For every force, there is an equal and opposite reaction force

tension

a pulling force that is transmitted through a rope, chain, or similar object

normal force

the force that acts in a direction that is perpendicular to the surface where two objects make contact

gravity

a field force that acts between themasses of any two objects

Newton’s Law of Universal Gravitation

states that gravity is a field force that acts between any two objects in the universe, the strength of this force varies in direct proportion to the masses of objects involved and inversely to the square of the distance between them

free fall acceleration on Pluto

0.58 m/seconds squared

free fall acceleration on Jupiter

25.89 m/seconds squared

weight

the force of gravity acting on the matter in an object

mass

the measure of the amount of matter in an object

friction

a contact force that works against the motion of objects trying to move past each other

static friction

the frictional force between two objects that are touching but not moving relative to each other

sliding friction

the frictional force between two objects when one is sliding past the other; aka kinetic friction

rolling friction

the frictional force between two objects when one is rolling relative to the other

centripetal force

the force that accelerates an object towards the center of a circular path

fundamental forces

any one of the four forces that appear to underlie all the other known forces: gravity, strong force, weak force, and electromagnetic force

traction

the frictional force between a vehicle’s tires and the road, responsible for accelerating the vehicle

strong force

the attractive forces that holds protons and neutrons together in a nucleus

weak forces

the extreme short-distance force that holds the subatomic particles together inside protons and neutrons

Weak Force vs Strong Force Strength comparison:

weak for is one millionth the strength of strong nuclear force

electromagnetic force

the force produced by static and moving charges

Electromagnetic Force vs Strong Force Strength Comparison

electromagnetic is 1/137 strength of strong nuclear force

static electricity

the accumulated charge on an object

electric force

the field force between two charged objects

electric field

a three dimensional region around a charged object that will apply a force on other charged objects within that region

electric potential energy

energy that is stored by a charged object in the electric field. The quantity depends on the magnitude of the charges and the object’s position in the field

charging by friction

the process by which an object can gain excess charge while being rubbed by another object

charging by conduction

the process by which one charged object can produce a second charged object by the two objects being placed in contact with each other and the excess charge being shared

charging by induction

the process by which one charged object can produce a second charged object by allowing the electric force to move excess charge onto the second object while the two objects are not in contact with each other

grounding

the act of providing a path for electrical charge to move into the earth

law of conservation of charge

the principle that states that charge cannot be created or destroyed but only transferred between objects

current electricity

electricity involving moving electric charges

electric current

the movement of electric charge through a complete loop

open circuit

an incomplete electric circuit that prevents the movement of charge

closed circuit

a complete electric circuit that allows charge to flow

direct current

electric current in which electric charges move only in one direction also known as DC.

conventional current

the direction in a DC circuit that positive charges would flow; decided by agreement as the standard current direction

alternating current

electric current in which the charge carriers change direction periodically

electrical conductor

a material through which electric charge moves easily

electrical insulator

a material through which electric charge does not move easily

semiconductor

a material with conductivity between those of conductors and insulators

ampere (A)

a fundamental SI unit of electric current

ammeter

a meter used to measure electric current though a circuit

voltage

the “force” that moves electric charge carriers through an electrical circuit; also called electric potential difference.

volt

derived SI unit for electrical potential difference equal to one joule per coulomb.

voltmeter

meter used to measure voltage

battery

a powers source for DC electrical device that slows down electric current of two or more electrochemical cells

resistor

an electrical device that slows down electric current by converting electrical energy into other forms, such as thermal energy

ohm

the derived SI unit for electrical resistance

electrical resistance (R)

an object’s opposition to the movement of charge carriers

superconductor

a material with zero resistance

Ohm’s Law

the law that states that the current in a circuit is directly related to the voltage and inversely related to the resistance

short circuit

an unintended path for an electric current

series circuit

a circuit with only on path that electric current can take

parallel circuit

a circuit with multiple paths that electric current can take

electric power

the work per second done or produced by electrical systems

fuse

an electrical safety device that opens the circuit by melting when an overheated condition occurs due to excessive current